subject:(ultrafast spectroscopy)

University of California – Berkeley

1. Schlau-Cohen, Gabriela Sadira. Multidimensional Spectroscopy of Photosynthetic Complexes.

Degree: Chemistry, 2011, University of California – Berkeley

URL: http://www.escholarship.org/uc/item/5j97q5cw

► Experiments using two-dimensional (2D) electronic spectroscopy to investigate the structure-function relationships that give rise to photosynthetic energy transfer within pigment protein complexes are presented and… (more)

▼ Experiments using two-dimensional (2D) electronic spectroscopy to investigate the structure-function relationships that give rise to photosynthetic energy transfer within pigment protein complexes are presented and discussed in this dissertation. 2D electronic spectroscopy using ultrafast laser pulses throughout the visible regime was applied to study excitation energy transfer in the major light harvesting complex of photosystem II (LHCII) and the reaction center from purple bacteria. These experiments elucidated information about the excited state structure and the energy transfer timescales within these complexes. All-parallel 2D spectroscopy was used to monitor the energy transfer dynamics in LHCII and reveals previously unobserved sub-100 fs energy transfer between the chlorophyll-b (Chl-b) and chlorophyll-a (Chl-a) bands and within the Chl-a band. Reproducing these results with simulations led to improvements in the values of the uncoupled transition energies of the chlorophyll in the working Hamiltonian of LHCII. The delocalized excited states observed in the experimental and theoretical results were found to increase the range of optimal angles for energy transfer from LHCII to neighboring pigment-protein complexes, as opposed to the case of a single, isolated donor excited state. Polarized 2D spectroscopy experiments reported here identified previously unresolved excitation energy transfer steps in LHCII. These results were used to determine the angle betweentransition dipole moments of the donor and acceptor. A new method was developed to use the angle between transition dipole moments to find the uncoupled transition energies of the chlorophyll, previously the major unknown for an accurate electronic Hamiltonian. This method was applied to LHCII. Quantum coherence, or a long-lived superposition of excited states, was observed in LHCII using a second polarization sequence. The observable timescales of coherence was determined to be 700-900 fs, which illustrates that quantum coherence lasts longer than many energy transfer steps. The potential contribution of coherence to the robustness of photosynthetic energy transfer to the rugged energy landscape and to temperature variations is discussed. Experiments on the B band of the bacterial reaction center were able to isolate the previously inseparable two peaks and observe energy transfer between these two excited states. A new extension of 2D spectroscopy, two-color 2D spectroscopy, was demonstrated forexamining the interactions between two spectrally separate chromophores. Using this approach, energy was found to transfer from the carotenoid to the bacteriochlorophyll both via S1 and via Qx in the bacterial reaction center in an approximately 2:1 ratio, and within about 750 fs.

Subjects/Keywords: Physical chemistry; Photosynthesis; Spectroscopy; Ultrafast

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APA (6^th Edition):

Schlau-Cohen, G. S. (2011). Multidimensional Spectroscopy of Photosynthetic Complexes. (Thesis). University of California – Berkeley. Retrieved from http://www.escholarship.org/uc/item/5j97q5cw

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Schlau-Cohen, Gabriela Sadira. “Multidimensional Spectroscopy of Photosynthetic Complexes.” 2011. Thesis, University of California – Berkeley. Accessed April 12, 2021. http://www.escholarship.org/uc/item/5j97q5cw.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Schlau-Cohen, Gabriela Sadira. “Multidimensional Spectroscopy of Photosynthetic Complexes.” 2011. Web. 12 Apr 2021.

Vancouver:

Schlau-Cohen GS. Multidimensional Spectroscopy of Photosynthetic Complexes. [Internet] [Thesis]. University of California – Berkeley; 2011. [cited 2021 Apr 12]. Available from: http://www.escholarship.org/uc/item/5j97q5cw.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Schlau-Cohen GS. Multidimensional Spectroscopy of Photosynthetic Complexes. [Thesis]. University of California – Berkeley; 2011. Available from: http://www.escholarship.org/uc/item/5j97q5cw

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Rice University

2. Anthonio, Bryan. Ultrafast Spectroscopy of (6,5) Carbon Nanotubes.

Degree: MS, Natural Sciences, 2020, Rice University

URL: http://hdl.handle.net/1911/107989

► Single-wall carbon nanotubes (SWCNTs) represent an exemplary model system for studying one-dimensional (1-D) physics in condensed matter research. Conceptually, they can be presented as a… (more)

Subjects/Keywords: optics; carbon nanotubes; spectroscopy; ultrafast

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APA (6^th Edition):

Anthonio, B. (2020). Ultrafast Spectroscopy of (6,5) Carbon Nanotubes. (Masters Thesis). Rice University. Retrieved from http://hdl.handle.net/1911/107989

Chicago Manual of Style (16^th Edition):

Anthonio, Bryan. “Ultrafast Spectroscopy of (6,5) Carbon Nanotubes.” 2020. Masters Thesis, Rice University. Accessed April 12, 2021. http://hdl.handle.net/1911/107989.

MLA Handbook (7^th Edition):

Anthonio, Bryan. “Ultrafast Spectroscopy of (6,5) Carbon Nanotubes.” 2020. Web. 12 Apr 2021.

Vancouver:

Anthonio B. Ultrafast Spectroscopy of (6,5) Carbon Nanotubes. [Internet] [Masters thesis]. Rice University; 2020. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/1911/107989.

Council of Science Editors:

Anthonio B. Ultrafast Spectroscopy of (6,5) Carbon Nanotubes. [Masters Thesis]. Rice University; 2020. Available from: http://hdl.handle.net/1911/107989

3. Li, Jiebo. Vibrational Energy Dissipation in Condensed Phases Investigated by Multiple Modes Multiple Dimensional Vibrational Spectroscopy.

Degree: PhD, Natural Sciences, 2014, Rice University

URL: http://hdl.handle.net/1911/88085

► The methodology of ultrafast multiple-mode multiple-dimensional vibrational spectroscopy has been developed and applied to investigate the vibrational energy dissipation in condensed phase. In particular, experiments… (more)

▼ The methodology of ultrafast multiple-mode multiple-dimensional vibrational spectroscopy has been developed and applied to investigate the vibrational energy dissipation in condensed phase. In particular, experiments have been focused on the studies of vibrational energy relaxation and mode-specific vibrational energy transfer in both heterogeneous and homogeneous phases. This thesis presents two distinctive vibrational energy dissipation pathways for molecules absorbed on the typical heterogeneous metal nanoparticle surfaces. On 2-10 nm platinum and palladium nanoparticles, it was found that the electronic excitation-mediated vibrational energy dissipation (~2ps) was at least one order magnitude faster than direct vibration-vibration relaxation (50ps). This electronic energy damping is accompanied by low frequency thermal energy generation on metallic surfaces. This electronic mediated pathway dominates until the electronic property of the particle is altered by reducing size to ~1nm. The energy relaxation pathway also could be altered by changing the chemical nature of the metallic nanoparticle. These findings are of fundamental importance to ultimately understanding the nature of heterogeneous catalysis. This thesis also demonstrates mode-specific vibrational energy exchange between ions in electrolyte solution. (i) Interactions between model molecules representing different building-blocks of proteins and thiocyanate anions in aqueous solutions are studied. The binding affinity between the thiocyanate anions and the charged amino acid residues is about 20 times bigger than that between water molecules and the amino acids, and about 5~10 times larger than that between the anions and neutral backbone amide groups. (ii) Ion segregation was also investigated by mode-specific vibrational energy exchange between thiocyanate anions. In aqueous solutions, it was found that “structure maker” ions, such as F-, would stay in the “water phase” and thereby promote aggregation of the SCN- in an “ionic phase”. “Structure breaker” ions, such as I-, would break the ionic SCN- phase. (iii) Mediated by combination band, vibrational energy flow down from thiocyanate to ammonium was used to confirm that ion pair is formed between ammonium and thiocyanate in aqueous solutions. Investigations of these microscopic structures and dynamics of aqueous salt solutions experiments will add depth to our understanding of general macroscopic properties of electrolyte solutions. Advisors/Committee Members: Zheng, Junrong (advisor), Kolomeisky, Anatoly B. (committee member), Kono, Junichiro (committee member).

Subjects/Keywords: Energy transfer; Ultrafast Infrared Spectroscopy

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APA (6^th Edition):

Li, J. (2014). Vibrational Energy Dissipation in Condensed Phases Investigated by Multiple Modes Multiple Dimensional Vibrational Spectroscopy. (Doctoral Dissertation). Rice University. Retrieved from http://hdl.handle.net/1911/88085

Chicago Manual of Style (16^th Edition):

Li, Jiebo. “Vibrational Energy Dissipation in Condensed Phases Investigated by Multiple Modes Multiple Dimensional Vibrational Spectroscopy.” 2014. Doctoral Dissertation, Rice University. Accessed April 12, 2021. http://hdl.handle.net/1911/88085.

MLA Handbook (7^th Edition):

Li, Jiebo. “Vibrational Energy Dissipation in Condensed Phases Investigated by Multiple Modes Multiple Dimensional Vibrational Spectroscopy.” 2014. Web. 12 Apr 2021.

Vancouver:

Li J. Vibrational Energy Dissipation in Condensed Phases Investigated by Multiple Modes Multiple Dimensional Vibrational Spectroscopy. [Internet] [Doctoral dissertation]. Rice University; 2014. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/1911/88085.

Council of Science Editors:

Li J. Vibrational Energy Dissipation in Condensed Phases Investigated by Multiple Modes Multiple Dimensional Vibrational Spectroscopy. [Doctoral Dissertation]. Rice University; 2014. Available from: http://hdl.handle.net/1911/88085

Rice University

4. Cong, Kankan. Coherent Light-Matter Coupling and Nonequilibrium Carrier Dynamics in Single-Chirality Carbon Nanotubes.

Degree: PhD, Natural Sciences, 2018, Rice University

URL: http://hdl.handle.net/1911/105639

► Single-wall carbon nanotubes (SWCNTs) are unique one-dimensional (1D) condensed matter systems in which strongly enhanced Coulomb interactions are combined with unusual band structure. There are… (more)

Subjects/Keywords: Ultrafast optical spectroscopy; Carbon nanotubes

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APA (6^th Edition):

Cong, K. (2018). Coherent Light-Matter Coupling and Nonequilibrium Carrier Dynamics in Single-Chirality Carbon Nanotubes. (Doctoral Dissertation). Rice University. Retrieved from http://hdl.handle.net/1911/105639

Chicago Manual of Style (16^th Edition):

Cong, Kankan. “Coherent Light-Matter Coupling and Nonequilibrium Carrier Dynamics in Single-Chirality Carbon Nanotubes.” 2018. Doctoral Dissertation, Rice University. Accessed April 12, 2021. http://hdl.handle.net/1911/105639.

MLA Handbook (7^th Edition):

Cong, Kankan. “Coherent Light-Matter Coupling and Nonequilibrium Carrier Dynamics in Single-Chirality Carbon Nanotubes.” 2018. Web. 12 Apr 2021.

Vancouver:

Cong K. Coherent Light-Matter Coupling and Nonequilibrium Carrier Dynamics in Single-Chirality Carbon Nanotubes. [Internet] [Doctoral dissertation]. Rice University; 2018. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/1911/105639.

Council of Science Editors:

Cong K. Coherent Light-Matter Coupling and Nonequilibrium Carrier Dynamics in Single-Chirality Carbon Nanotubes. [Doctoral Dissertation]. Rice University; 2018. Available from: http://hdl.handle.net/1911/105639

University of Texas – Austin

5. -8757-3113. Studying the Density of States of buried interfaces in organic semiconductor thin films using electronic sum frequency generation.

Degree: PhD, Chemistry, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/2197

► Abstract: New nanostructured semiconductor materials such as nanocrystals and organic semiconductors constitute an attractive platform for optoelectronics design due to the ease of their processability… (more)

▼ Abstract: New nanostructured semiconductor materials such as nanocrystals and organic semiconductors constitute an attractive platform for optoelectronics design due to the ease of their processability and highly tunable properties. Incorporating these new nanostructured materials into electrical circuits requires forming junctions between them and other layers in a device, yet the change in dielectric properties about these junctions can strongly perturb the electronic structure of the two layers. Specifically, the morphology of the interface between two materials greatly affect their ability to transfer charge and energy through the system, and the method through which this energy travels across a junction is poorly understood. To study these processes, an interfacial technique is required that measures the Density of States (Dos) at buried interfaces in working devices. In this thesis, we adapt an interface-selective optical technique, electronic sum frequency generation (ESFG), to study the dynamics of energy transfer across interfaces in these materials. We begin by developing “direct” detected ESFG to study the electronic states and morphology at the interface of thin films made from known organic semiconductor materials. Using direct ESFG, we examine the differences in the DoS at an interface in an organic thin film relative to its bulk. Through polarization optics, we study morphological changes in the film caused at the junction of the OSC and substrate. To account for interference from multiple ESFG active interfaces present in a thin film, we use a modeling system to separate contributions to the measured ESFG signal from the air exposed and buried interface of interest. We then adapt the direct detected ESFG to “heterodyne” detected ESFG (HD-ESFG), which significantly increases the detection ability of the ESFG spectrometer. Additionally, HD-ESFG allows us to measure the phase of the materials response, which direct ESFG cannot. This phase information can give a better understanding of the morphology at the interface and additional inputs for thin film interference modeling to better deconvolute the signal from the buried interface. Advisors/Committee Members: Roberts, Sean T. (advisor), Baiz, Carls R (committee member), Vanden Bout, David A (committee member), Rose, Michael (committee member), Li, Xiaoqin (committee member).

Subjects/Keywords: Spectroscopy; Ultrafast; ESFG; Interfaces

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APA (6^th Edition):

-8757-3113. (2019). Studying the Density of States of buried interfaces in organic semiconductor thin films using electronic sum frequency generation. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/2197

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-8757-3113. “Studying the Density of States of buried interfaces in organic semiconductor thin films using electronic sum frequency generation.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed April 12, 2021. http://dx.doi.org/10.26153/tsw/2197.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-8757-3113. “Studying the Density of States of buried interfaces in organic semiconductor thin films using electronic sum frequency generation.” 2019. Web. 12 Apr 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-8757-3113. Studying the Density of States of buried interfaces in organic semiconductor thin films using electronic sum frequency generation. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Apr 12]. Available from: http://dx.doi.org/10.26153/tsw/2197.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-8757-3113. Studying the Density of States of buried interfaces in organic semiconductor thin films using electronic sum frequency generation. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/2197

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Minnesota

6. Brooks, James. Surface-Enhanced Raman Spectroscopy as a Probe to Understand Plasmon-Mediated Photochemistry.

Degree: PhD, Chemistry, 2019, University of Minnesota

URL: http://hdl.handle.net/11299/217170

► The development of plasmonic nanostructures as light-activated photocatalysts has proven to be a promising research avenue due to their ability to access and drive unfavorable… (more)

▼ The development of plasmonic nanostructures as light-activated photocatalysts has proven to be a promising research avenue due to their ability to access and drive unfavorable chemical reactions. Theses chemical reactions are fueled by the presence of surface plasmons, which are the collective oscillation of the free electron density on the material’s surface. Once a surface plasmon is photoexcited, their initial energy rapidly decays into multiple different pathways, such as enhanced electromagnetic fields, an abundance of hot carriers, and dramatically elevated local thermal environments. To better understand the various chemistries that are enabled by plasmonic materials and the associated mechanisms driving these processes, we have employed surface-enhanced Raman spectroscopy to interrogate a plethora of plasmon-molecule coupled systems. Our initial studies investigated the relationship between the plasmonic local fields and a well-established plasmon-driven photochemical reaction. We found that there were no observable correlations between the two in our studies and identified a competing degradation pathway for the studied analytes. In addition to exploring well-studied plasmon-induced chemical photoreactions, we have highlighted two new reactions that were accessed on the gold film-over-nanosphere substrates. First, we were able to induce and subsequently monitor a selective intramolecular methyl migration on N-methylpyridinium using surface-enhanced Raman spectroscopy. This work emphasizes the growing potential of initiating highly-selective chemistries with plasmonic materials for synthetic or redox purposes. The second previously unreported plasmon-driven reaction involves the double cleavage of the C-N bond on a pair of viologen derivatives. While these viologens have traditionally been employed as robust redox species, the unique and highly-powerful plasmonic local fields allowed the viologens to access an entirely new reaction pathway to transform into 4,4’-bipyridine. Lastly, we discuss our experimental approaches towards transiently studying the mechanism behind plasmon-mediated hot electron transfer. Using ultrafast surface-enhanced Raman spectroscopy, we interrogated the transient dynamics that occurred between surface plasmons and a bevy of electron accepting chemical adsorbates. Ultimately, the primary goal of this work is to provide a quantitative description of the transient interactions, which will assist in increasing the reported efficiencies and yields of plasmon-mediated chemical reaction and inspire the rational design of plasmonically-powered devices.

Subjects/Keywords: Plasmonics; SERS; Spectroscopy; Ultrafast

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APA (6^th Edition):

Brooks, J. (2019). Surface-Enhanced Raman Spectroscopy as a Probe to Understand Plasmon-Mediated Photochemistry. (Doctoral Dissertation). University of Minnesota. Retrieved from http://hdl.handle.net/11299/217170

Chicago Manual of Style (16^th Edition):

Brooks, James. “Surface-Enhanced Raman Spectroscopy as a Probe to Understand Plasmon-Mediated Photochemistry.” 2019. Doctoral Dissertation, University of Minnesota. Accessed April 12, 2021. http://hdl.handle.net/11299/217170.

MLA Handbook (7^th Edition):

Brooks, James. “Surface-Enhanced Raman Spectroscopy as a Probe to Understand Plasmon-Mediated Photochemistry.” 2019. Web. 12 Apr 2021.

Vancouver:

Brooks J. Surface-Enhanced Raman Spectroscopy as a Probe to Understand Plasmon-Mediated Photochemistry. [Internet] [Doctoral dissertation]. University of Minnesota; 2019. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/11299/217170.

Council of Science Editors:

Brooks J. Surface-Enhanced Raman Spectroscopy as a Probe to Understand Plasmon-Mediated Photochemistry. [Doctoral Dissertation]. University of Minnesota; 2019. Available from: http://hdl.handle.net/11299/217170

Colorado State University

7. Tracy, Kathryn Marie. Visualizing dynamics using 100 kHz 2D IR spectroscopy and microscopy.

Degree: PhD, Chemistry, 2018, Colorado State University

URL: http://hdl.handle.net/10217/191357

► 2D IR spectroscopy is a nonlinear optical method with the ability to characterize condensed phase chemical systems. It offers information regarding structure and dynamics of… (more)

Subjects/Keywords: ultrafast dynamics; ultrafast spectroscopy; OPCPA; 2D IR microscopy; ultrafast lasers; 2D IR spectroscopy

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APA (6^th Edition):

Tracy, K. M. (2018). Visualizing dynamics using 100 kHz 2D IR spectroscopy and microscopy. (Doctoral Dissertation). Colorado State University. Retrieved from http://hdl.handle.net/10217/191357

Chicago Manual of Style (16^th Edition):

Tracy, Kathryn Marie. “Visualizing dynamics using 100 kHz 2D IR spectroscopy and microscopy.” 2018. Doctoral Dissertation, Colorado State University. Accessed April 12, 2021. http://hdl.handle.net/10217/191357.

MLA Handbook (7^th Edition):

Tracy, Kathryn Marie. “Visualizing dynamics using 100 kHz 2D IR spectroscopy and microscopy.” 2018. Web. 12 Apr 2021.

Vancouver:

Tracy KM. Visualizing dynamics using 100 kHz 2D IR spectroscopy and microscopy. [Internet] [Doctoral dissertation]. Colorado State University; 2018. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/10217/191357.

Council of Science Editors:

Tracy KM. Visualizing dynamics using 100 kHz 2D IR spectroscopy and microscopy. [Doctoral Dissertation]. Colorado State University; 2018. Available from: http://hdl.handle.net/10217/191357

Victoria University of Wellington

8. Djorović, Aleksa. Single Shot Time-Resolved Terahertz Spectroscopy for Optoelectronic Materials.

Degree: 2018, Victoria University of Wellington

URL: http://hdl.handle.net/10063/7065

► Optoelectronic materials and devices, such as LEDs and solar cells, are ubiquitous in the modern, technologically driven world. Understanding the fundamental physical process in optoelectronic… (more)

▼ Optoelectronic materials and devices, such as LEDs and solar cells, are ubiquitous in the modern, technologically driven world. Understanding the fundamental physical process in optoelectronic materials is essential for the design and development of new devices which are more efficient, cheaper, printable, as well as environmentally friendly. Two particularly important material properties for device performance are charge mobility and photoconductivity, as they increase charge separation and extraction efficiencies, and thus give specific insight into device efficiency. The best suited technique for measuring mobility and conductivity on ultrafast timescales is Terahertz spectroscopy. Terahertz spectroscopy is a non-invasive, contact-free probe of the mobility of charges in optoelectronic materials. Terahertz time-domain spectroscopy allows for the direct determination of the entire complex-valued conductivity. As a result, important optical properties such as the complex refractive index and dielectric function of a material can be measured directly. The short duration of THz pulses, on the order of 1 ps, also allows for time-resolved studies of the transient photoconductivity in optically-excited materials with sub-picosecond time resolution, i.e. Time-Resolved Teraherz Spectroscopy (TRTS). Traditionally, only the peak of the THz pulse signal is measured with TRTS, due to the time constraints of a two-delay experiment. This does not allow for frequency-resolved THz spectra. As a result, it discards a lot of the information Terahertz-TDS spectroscopy contains, as well as its advantages over other spectroscopic techniques. Frequency-resolved TRTS would allow for the calculation of transient conductivity at each pump-probe delay time and can differentiate between signals of excitons and free charge carriers. This would allow for robust interpretations of charge mobility in novel materials. However, frequency-resolved TRTS is not practically feasible in a dual-delay configuration. We develop in this thesis a novel single-shot method based on angle-to-time mapping of a rotating probe. This method is applied to build a single-shot Terahertz-TDS spectrometer. A transmissive grating applies pulse front tilt which allows for the measurement of the entire THz transient (over a 5.7 ps window) in a single laser shot on a CMOS multichannel detector, thus alleviating the need for delay stage sampling of the THz transient, and leading to a reduction of experimental time by several orders of magnitude. An optical pump excitation is incorporated to allow a time-resolved measurement (TRTS) of the entire terahertz time-domain spectrum, and thus frequency-resolved TRTS. We show qualitative agreement between the THz time domain spectra obtained with the single shot technique and the standard free-space electro-optic (EO) sampling with balanced photodiodes, with an order of magnitude increased signal sensitivity. A proof-of-concept single shot TRTS study of a Si semiconductor sample is also given, showing we are able to resolve the TRTS… Advisors/Committee Members: Hodgkiss, Justin.

Subjects/Keywords: Terahertz; Ultrafast spectroscopy; Time-resolved spectroscopy

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APA (6^th Edition):

Djorović, A. (2018). Single Shot Time-Resolved Terahertz Spectroscopy for Optoelectronic Materials. (Masters Thesis). Victoria University of Wellington. Retrieved from http://hdl.handle.net/10063/7065

Chicago Manual of Style (16^th Edition):

Djorović, Aleksa. “Single Shot Time-Resolved Terahertz Spectroscopy for Optoelectronic Materials.” 2018. Masters Thesis, Victoria University of Wellington. Accessed April 12, 2021. http://hdl.handle.net/10063/7065.

MLA Handbook (7^th Edition):

Djorović, Aleksa. “Single Shot Time-Resolved Terahertz Spectroscopy for Optoelectronic Materials.” 2018. Web. 12 Apr 2021.

Vancouver:

Djorović A. Single Shot Time-Resolved Terahertz Spectroscopy for Optoelectronic Materials. [Internet] [Masters thesis]. Victoria University of Wellington; 2018. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/10063/7065.

Council of Science Editors:

Djorović A. Single Shot Time-Resolved Terahertz Spectroscopy for Optoelectronic Materials. [Masters Thesis]. Victoria University of Wellington; 2018. Available from: http://hdl.handle.net/10063/7065

Iowa State University

9. Vaswani, Chirag. Terahertz driven quantum and coherent dynamics: From superconductors to topological materials.

Degree: 2020, Iowa State University

URL: https://lib.dr.iastate.edu/etd/18417

► Rapid developments in ultrafast laser technology over the past decade have enabled the generation of strong ultrashort pulses spanning the entire electromagnetic spectrum. Nonlinear excitation… (more)

Subjects/Keywords: Superconductivity; Terahertz spectroscopy; Topological semimetals; Ultrafast spectroscopy

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APA (6^th Edition):

Vaswani, C. (2020). Terahertz driven quantum and coherent dynamics: From superconductors to topological materials. (Thesis). Iowa State University. Retrieved from https://lib.dr.iastate.edu/etd/18417

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Vaswani, Chirag. “Terahertz driven quantum and coherent dynamics: From superconductors to topological materials.” 2020. Thesis, Iowa State University. Accessed April 12, 2021. https://lib.dr.iastate.edu/etd/18417.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Vaswani, Chirag. “Terahertz driven quantum and coherent dynamics: From superconductors to topological materials.” 2020. Web. 12 Apr 2021.

Vancouver:

Vaswani C. Terahertz driven quantum and coherent dynamics: From superconductors to topological materials. [Internet] [Thesis]. Iowa State University; 2020. [cited 2021 Apr 12]. Available from: https://lib.dr.iastate.edu/etd/18417.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Vaswani C. Terahertz driven quantum and coherent dynamics: From superconductors to topological materials. [Thesis]. Iowa State University; 2020. Available from: https://lib.dr.iastate.edu/etd/18417

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Michigan

10. Kiefer, Laura. Ultrafast Spectral Dynamics of a Rhenium Photocatalyst.

Degree: PhD, Chemistry, 2016, University of Michigan

URL: http://hdl.handle.net/2027.42/135909

► This dissertation investigates the photo-initiated CO2 reduction catalyst, Re(bpy)(CO)3Cl, in multiple states along the photocatalytic cycle with the goal of understanding the influence of electrostatics… (more)

▼ This dissertation investigates the photo-initiated CO2 reduction catalyst, Re(bpy)(CO)3Cl, in multiple states along the photocatalytic cycle with the goal of understanding the influence of electrostatics and solvent on each step. Two-dimensional infrared (2DIR) spectroscopy was used to characterize the electronic ground state dynamics of the Re photocatalyst, including several derivatives, in multiple solvents. Though insensitive to the substituents, spectral dynamics do correlate with the solvent's nucleophilicity. Transient-2DIR experiments enabled the first ever characterization of a quasi-equilibrated electronic excited state. Electronic excitation at 400 nm followed by equilibration in the triplet metal-to-ligand charge transfer state, provided direct access to dynamics using a time-delayed 2DIR pulse sequence. Relative to the ground state, we observe a two-fold slowdown in spectral dynamics as sensed by the in-phase symmetric vibrational mode and a decrease in the vibrational lifetime by a factor of five. Transient 2DIR characterizes catalytically relevant, long-lived electronic excited states independent of any ground state dynamics. Introducing the sacrificial electron donor triethanolamine (TEOA) revealed a concentration dependent slowdown of the Re spectral dynamics, indicating both preferential solvation and solvent exchange. Preferential solvation was confirmed after UV-Vis pump/IR probe experiments showed the appearance of the singly reduced, intermolecular electron transfer product on a timescale faster than diffusion (<70 ps). This result highlights a previously ignored mechanistic aspect of this essential electron transfer reaction. Re photocatalysis experiments were supplemented by additional investigations into solvation and molecular flexibility. In a solution of the Re complex and Na+SCN- in THF, 2DIR experiments revealed an intermolecular vibrational energy transfer between the Re complex and Na+SCN- on a timescale distinct from the equilibrium fluctuations of the two individual donor and acceptor bands involved, indicating non-Gaussian dynamics. The next work isolated polymer flexibility chosen specifically because of its site-specific vibrational probes. The chain ends spectrally diffuse slower than do the inner chain sites and going from dilute solution to a solvent-free film, the heterogeneity in site dynamics become reduced due to the crowding influence of neighboring molecules. This experiment was supported with a coarse grained model of the polymer which showed essentially quantitative agreement with measured relative dynamics. Advisors/Committee Members: Kubarych, Kevin Joel (committee member), Sih, Vanessa (committee member), Geva, Eitan (committee member), Sension, Roseanne J (committee member).

Subjects/Keywords: ultrafast dynamics; photocatalyst; infrared spectroscopy; Chemistry; Science

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APA (6^th Edition):

Kiefer, L. (2016). Ultrafast Spectral Dynamics of a Rhenium Photocatalyst. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/135909

Chicago Manual of Style (16^th Edition):

Kiefer, Laura. “Ultrafast Spectral Dynamics of a Rhenium Photocatalyst.” 2016. Doctoral Dissertation, University of Michigan. Accessed April 12, 2021. http://hdl.handle.net/2027.42/135909.

MLA Handbook (7^th Edition):

Kiefer, Laura. “Ultrafast Spectral Dynamics of a Rhenium Photocatalyst.” 2016. Web. 12 Apr 2021.

Vancouver:

Kiefer L. Ultrafast Spectral Dynamics of a Rhenium Photocatalyst. [Internet] [Doctoral dissertation]. University of Michigan; 2016. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/2027.42/135909.

Council of Science Editors:

Kiefer L. Ultrafast Spectral Dynamics of a Rhenium Photocatalyst. [Doctoral Dissertation]. University of Michigan; 2016. Available from: http://hdl.handle.net/2027.42/135909

University of Michigan

11. Daley, Kimberly. Solvation Dynamics of Concentrated Aqueous Polymer Mixtures: A Two Dimensional Infrared Spectroscopy Study.

Degree: PhD, Chemistry, 2018, University of Michigan

URL: http://hdl.handle.net/2027.42/147552

► Water-solute interactions still remain a challenge to study experimentally, though they are critical to protein and biomacromolecule stability, structure, and function. Hydration dynamics at interfaces… (more)

Subjects/Keywords: ultrafast spectroscopy; macromolecular crowding; Chemistry; Science

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APA (6^th Edition):

Daley, K. (2018). Solvation Dynamics of Concentrated Aqueous Polymer Mixtures: A Two Dimensional Infrared Spectroscopy Study. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/147552

Chicago Manual of Style (16^th Edition):

Daley, Kimberly. “Solvation Dynamics of Concentrated Aqueous Polymer Mixtures: A Two Dimensional Infrared Spectroscopy Study.” 2018. Doctoral Dissertation, University of Michigan. Accessed April 12, 2021. http://hdl.handle.net/2027.42/147552.

MLA Handbook (7^th Edition):

Daley, Kimberly. “Solvation Dynamics of Concentrated Aqueous Polymer Mixtures: A Two Dimensional Infrared Spectroscopy Study.” 2018. Web. 12 Apr 2021.

Vancouver:

Daley K. Solvation Dynamics of Concentrated Aqueous Polymer Mixtures: A Two Dimensional Infrared Spectroscopy Study. [Internet] [Doctoral dissertation]. University of Michigan; 2018. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/2027.42/147552.

Council of Science Editors:

Daley K. Solvation Dynamics of Concentrated Aqueous Polymer Mixtures: A Two Dimensional Infrared Spectroscopy Study. [Doctoral Dissertation]. University of Michigan; 2018. Available from: http://hdl.handle.net/2027.42/147552

Vanderbilt University

12. Jarrahi, Zeynab. Effect of Substrate and Morphology on the Relaxation Dynamics of Carriers and Phonons in Graphene.

Degree: PhD, Physics, 2016, Vanderbilt University

URL: http://hdl.handle.net/1803/12764

► Graphene, the two dimensional allotrope of the carbon family, exhibits extremely high electron mobility, thermal conductivity and fascinating ultrafast carrier-carrier and carrier-phonons interactions. However, being… (more)

▼ Graphene, the two dimensional allotrope of the carbon family, exhibits extremely high electron mobility, thermal conductivity and fascinating ultrafast carrier-carrier and carrier-phonons interactions. However, being merely one atom thick, introducing a substrate or altering the morphological form of graphene can affect both its equilibrium and non-equilibrium dynamics and inevitably influence the performance of graphene-based devices. In the first part of this dissertation, we use fluence and energy dependent ultrafast pump-probe spectroscopy to determine the effect of substrate on the femtosecond transient electron and phonon dynamics of single layer graphene transferred on sapphire, quartz and single crystalline diamond. Using a multi-channel cooling theory involving surface phonons of the substrate, intrinsic optical phonons of graphene and the corresponding competing scattering rates, we proceed to explain the strong substrate-dependent dynamics of graphene observed in our experiments. We stipulate that the sub-nm surface roughness of the studied substrates, enable a strong coupling between the phototexcited carriers in graphene and the surface vibrational modes of the polar substrates. We show that this additional energy relaxation pathway can compete with the intrinsic phonons of graphene to not only reduce the transient electron temperature but also the carrier and optical phonon lifetimes in graphene. In the second part of this dissertation, we introduce a methodology for fabrication of a novel quasi-one dimensional morphology of graphene called curled graphene ribbons (CGR). Our gate dependent scanning photocurrent measurements reveal an astounding two orders of magnitude enhancement in the photocurrent response of CGR which we attributed to the photothermoelectric effect (PTE).Understanding how the equilibrium and non-equilibrium dynamics of carriers and phonons in graphene are altered by the interface or morphology and deciphering the various energy relaxation pathways, will pave the way towards realization of higher performance graphene based electronics and optoelectronics. Advisors/Committee Members: Kalman Varga (committee member), Volker Oberacker (committee member), Jim Davidson (committee member), Richard Mu (committee member), Norman Tolk (Committee Chair).

Subjects/Keywords: Interface; Surface phonons; Optoelectronics; Graphene; Ultrafast Spectroscopy

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APA (6^th Edition):

Jarrahi, Z. (2016). Effect of Substrate and Morphology on the Relaxation Dynamics of Carriers and Phonons in Graphene. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/12764

Chicago Manual of Style (16^th Edition):

Jarrahi, Zeynab. “Effect of Substrate and Morphology on the Relaxation Dynamics of Carriers and Phonons in Graphene.” 2016. Doctoral Dissertation, Vanderbilt University. Accessed April 12, 2021. http://hdl.handle.net/1803/12764.

MLA Handbook (7^th Edition):

Jarrahi, Zeynab. “Effect of Substrate and Morphology on the Relaxation Dynamics of Carriers and Phonons in Graphene.” 2016. Web. 12 Apr 2021.

Vancouver:

Jarrahi Z. Effect of Substrate and Morphology on the Relaxation Dynamics of Carriers and Phonons in Graphene. [Internet] [Doctoral dissertation]. Vanderbilt University; 2016. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/1803/12764.

Council of Science Editors:

Jarrahi Z. Effect of Substrate and Morphology on the Relaxation Dynamics of Carriers and Phonons in Graphene. [Doctoral Dissertation]. Vanderbilt University; 2016. Available from: http://hdl.handle.net/1803/12764

Penn State University

13. Li, Xiang. Ultrafast Charge Transfer �in Conventional Solvent �and Ionic Liquids .

Degree: 2011, Penn State University

URL: https://submit-etda.libraries.psu.edu/catalog/11674

► This thesis work is aimed at understanding ultrafast intermolecular electron transfer and solvation processes in conventional solvents and ionic liquids. Following a brief introduction in… (more)

▼ This thesis work is aimed at understanding ultrafast intermolecular electron transfer and solvation processes in conventional solvents and ionic liquids. Following a brief introduction in Chapter 1, Chapter 2 explains the main experimental techniques and data analysis methods used in this thesis. Chapter 3 and Chapter 4 are focused on charge transfer reactions in representative ionic liquids in comparison to conventional solvents. Chapter 5 carefully examines a selected system for studying dynamic heterogeneity studies in ionic liquids. Charge transfer is an important step in many types of chemical and biochemical reactions. The energetics and rates of charge transfer are greatly affected by the polarity and dynamics of the surrounding medium and extensive research has explored the effect of polar solvents on charge transfer. In contrast, despite the large amount of attention on ionic liquids for many applications, few studies have focused on fundamental aspects of charge transfer ionic liquids. I have surveyed the behavior of several solvent-controlled intramolecular charge transfer reactions in representative ionic liquids and compared it to what is found for these same reactions in conventional dipolar solvents using time-resolved fluorescence spectroscopy. In chapter 3, crystal violet lactone (CVL), which exhibits distinct dual emission in fluid solution as a result of a rapid excited-state charge transfer reaction, was measured in series of conventional solvents as background for ionic liquids studies. Solvatochromic analysis using a dielectric continuum model suggests dipole moments of 9-12 D for the initially excited (LE) state and ~24 D for the charge-transfer (CT) state. Intensities of steady-state emission as well as kinetic data provide free energies for the LE → CT reaction that range from +12 kJ/mol in nonpolar solvents to -10 kJ/mol in highly polar solvents at 25 C. Reaction rates constants, which lie in the range of 10-100 ns-1 in most solvents, depend on both solvent polarity and solvent friction. In highly polar solvents, this charge transfer reaction was confirmed to follow two-state kinetics as used in typical dual fluorescence probes like aminobenzonitriles. Reaction rates are correlated to solvation times in a manner that indicates the reaction is a solvent-controlled electron transfer on an adiabatic potential surface having a modest barrier. In Chapter 4, the charge transfer reaction of CVL was studied in ionic liquids. Compared with conventional solvents, the reaction is much more complicated. Equilibrium is not reached in any ionic liquid due to the much slower reaction. Furthermore, in two other well-studied charge transfer probes in several classes of ionic liquids, we also found the reaction kinetics are typically more complicated. Multi-exponential decays are observed when reaction times are comparable to solvation times, which are on the nanosecond scale in most ionic liquids at room temperature. Time-resolved spectra were dissected into LE and CT states… Advisors/Committee Members: Mark Maroncelli, Dissertation Advisor/Co-Advisor, Mark Maroncelli, Committee Chair/Co-Chair, Tom Mallouk, Committee Member, John B Asbury, Committee Member, John H Golbeck, Committee Member.

Subjects/Keywords: Ultrafast Fluorescence Spectroscopy; Ionic Liquids; Charge Transfer

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APA (6^th Edition):

Li, X. (2011). Ultrafast Charge Transfer �in Conventional Solvent �and Ionic Liquids . (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/11674

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Li, Xiang. “Ultrafast Charge Transfer �in Conventional Solvent �and Ionic Liquids .” 2011. Thesis, Penn State University. Accessed April 12, 2021. https://submit-etda.libraries.psu.edu/catalog/11674.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Li, Xiang. “Ultrafast Charge Transfer �in Conventional Solvent �and Ionic Liquids .” 2011. Web. 12 Apr 2021.

Vancouver:

Li X. Ultrafast Charge Transfer �in Conventional Solvent �and Ionic Liquids . [Internet] [Thesis]. Penn State University; 2011. [cited 2021 Apr 12]. Available from: https://submit-etda.libraries.psu.edu/catalog/11674.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Li X. Ultrafast Charge Transfer �in Conventional Solvent �and Ionic Liquids . [Thesis]. Penn State University; 2011. Available from: https://submit-etda.libraries.psu.edu/catalog/11674

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Newcastle

14. Duck, Benjamin Clyde. Methods and materials for the investigation and extension of the performance of polymer photovoltaic devices.

Degree: PhD, 2011, University of Newcastle

URL: http://hdl.handle.net/1959.13/923581

►

Research Doctorate - Doctor of Philosophy (PhD)

The focus of this thesis is on developing new experimental techniques for the study of charge generation in… (more)

▼

Research Doctorate - Doctor of Philosophy (PhD)

The focus of this thesis is on developing new experimental techniques for the study of charge generation in conducting polymers and exploring the low energy response of photovoltaic devices constructed from these semiconducting materials. The behaviour of photonic crystal fibre when pumped with femtosecond pulses sourced from a Ti:Sapphire system is characterised. Higher order mode structures within the output are observed for pumping wavelengths that lie below the group velocity dispersion zero of the fibre. Enhancement of the higher order mode structure is shown to occur when the pumping position is offset from the centre of the fibre core. A novel investigation technique is employed where the output of the fibre is simultaneously spatially and spectrally measured to obtain accurate and detailed information about the wavelength dependence of the structures. The higher order features are determined to originate from solitons formed in a higher order mode within the fibre. An additional rotational component is observed, with the new measurement technique, which is attributed to the geometry of the fibre itself. The commonly available conducting polymer blends of MEH-PPV:PCBM and P3HT:PCBM are investigated for their performance at energies below the absorption range of the component materials in isolation. So called charge transfer (CT) state absorption is shown in only the blended systems and is observed to result in photocurrent generation at energies as low as 1.16 eV when the blend is used as the active layer in a photovoltaic device. A response at these energies makes them a viable candidate for near infrared photodetector applications. Photocurrent action spectroscopy measurements show that the CT response of MEH-PPV:PCBM blends matches the performance of the overall response however the P3HT:PCBM devices show a different behaviour for excitation in the two regions. The CT response is correlated with the film morphology and, in-particular, is related to the total number of absorption sites available. For P3HT:PCBM devices, annealing affects the film morphology, increasing the amount of phase segregation in the film, and thus diminishes the CT absorption while improving overall response. Modelling of the energy of the CT state is performed to analyse the affect of composition and annealing. MEH-PPV:PCBM devices show a reduction in the energy of the CT state for increasing concentrations of PCBM, a result which agrees with the annealing results obtained in P3HT:PCBM, however this is not reflected in the P3HT:PCBM composition data. The discrepancy indicates that the P3HT:PCBM system has two competing processes determining the energy of the CT state. Characterisation of the performance of the new low bandgap polymer material pC6TP is performed when incorporated into photovoltaic devices. Binary blends of pC6TP:PCBM are shown to respond to annealing only when a low boiling point solvent is used and by varying the blend composition it is shown that a ratio of 1:2…

Advisors/Committee Members: University of Newcastle. Faculty of Science and Information Technology, School of Mathematical and Physical Sciences.

Subjects/Keywords: polymer photovoltaic; ultrafast spectroscopy; microstructured optical fibre

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Duck, B. C. (2011). Methods and materials for the investigation and extension of the performance of polymer photovoltaic devices. (Doctoral Dissertation). University of Newcastle. Retrieved from http://hdl.handle.net/1959.13/923581

Chicago Manual of Style (16^th Edition):

Duck, Benjamin Clyde. “Methods and materials for the investigation and extension of the performance of polymer photovoltaic devices.” 2011. Doctoral Dissertation, University of Newcastle. Accessed April 12, 2021. http://hdl.handle.net/1959.13/923581.

MLA Handbook (7^th Edition):

Duck, Benjamin Clyde. “Methods and materials for the investigation and extension of the performance of polymer photovoltaic devices.” 2011. Web. 12 Apr 2021.

Vancouver:

Duck BC. Methods and materials for the investigation and extension of the performance of polymer photovoltaic devices. [Internet] [Doctoral dissertation]. University of Newcastle; 2011. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/1959.13/923581.

Council of Science Editors:

Duck BC. Methods and materials for the investigation and extension of the performance of polymer photovoltaic devices. [Doctoral Dissertation]. University of Newcastle; 2011. Available from: http://hdl.handle.net/1959.13/923581

University of Ottawa

15. Barlow, Aaron M. Spectral Distortions & Enhancements In Coherent Anti-Stokes Raman Scattering Hyperspectroscopy .

Degree: 2015, University of Ottawa

URL: http://hdl.handle.net/10393/32388

► Coherent anti-Stokes Raman scattering microscopy is a versatile technique for label-free imaging and spectroscopy of systems of biophysical interest. Due to the coherent nature of… (more)

Subjects/Keywords: Spectroscopy; Nonlinear optics; Microscopy; Ultrafast optics

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APA (6^th Edition):

Barlow, A. M. (2015). Spectral Distortions & Enhancements In Coherent Anti-Stokes Raman Scattering Hyperspectroscopy . (Thesis). University of Ottawa. Retrieved from http://hdl.handle.net/10393/32388

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Barlow, Aaron M. “Spectral Distortions & Enhancements In Coherent Anti-Stokes Raman Scattering Hyperspectroscopy .” 2015. Thesis, University of Ottawa. Accessed April 12, 2021. http://hdl.handle.net/10393/32388.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Barlow, Aaron M. “Spectral Distortions & Enhancements In Coherent Anti-Stokes Raman Scattering Hyperspectroscopy .” 2015. Web. 12 Apr 2021.

Vancouver:

Barlow AM. Spectral Distortions & Enhancements In Coherent Anti-Stokes Raman Scattering Hyperspectroscopy . [Internet] [Thesis]. University of Ottawa; 2015. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/10393/32388.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Barlow AM. Spectral Distortions & Enhancements In Coherent Anti-Stokes Raman Scattering Hyperspectroscopy . [Thesis]. University of Ottawa; 2015. Available from: http://hdl.handle.net/10393/32388

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

16. Su, Man-Nung. Optical Properties and Ultrafast Electron Dynamics in Gold, Aluminum and Hybrid Nanomaterials.

Degree: PhD, Natural Sciences, 2018, Rice University

URL: http://hdl.handle.net/1911/105844

► Novel nanomaterials have been attracting numerous attention for their enhanced properties which lead to many potential applications. Plasmonic nanostructures, supported by surface plasmon resonances, possess… (more)

▼ Novel nanomaterials have been attracting numerous attention for their enhanced properties which lead to many potential applications. Plasmonic nanostructures, supported by surface plasmon resonances, possess efficient hot carrier generation and manipulatable optical properties and are great candidates for applications such as solar cells, photocatalysis, etc. To efficiently utilize these properties in real-life applications, a fundamental understanding of the optical properties is necessary. In this dissertation, I study the optical properties and ultrafast electron dynamics of novel nanomaterials, including gold nanostructures fabricated by lithography, aluminum nanostructures as emerging plasmonic nanomaterials, and hybrid nanostructures including gold nanoblock dimers and “hedgehog” particles. I utilize single-particle spectroscopy combined with pump-probe transient extinction spectroscopy as a powerful tool to resolve the structural-optical relationship for nanomaterials. In the first part of the dissertation, the optomechanics of lithographically fabricated nanostructures are investigated for their advantages of better control on the size, shape, and material composition. I reveal the roles of adhesion layers and polycrystallinity in lithographically fabricated gold nanostructures on their acoustic vibrations. The thickness of the very thin adhesion layers greatly impacts the acoustic vibration frequencies. The vibration damping channel is dominated by the polycrystallinity. Lithography also supports nanoparticle clusters with precise interparticle geometry control. Taking advantage of this, I discover a mechanical coupling though substrates in such gold nanoparticle cluster. This mechanical coupling is a breakdown of classical continuum elastic theory. In the second part of the dissertation, aluminum nanostructures are studied as a great alternative to noble metals for their wider spectral tunability and lower cost. I investigate their ultrafast dynamics and reveal the effects of their native oxide layers and unique Drude-like electron structure on their optomechanical and optical response. The native oxide layer could be a key for longer-lived hot electrons through trapping at the core/shell interface. In the third part of the thesis, I studied the steady-state optical properties of composite nanostructures. Gold nanoblock dimers with edge-to-edge configurations possess strong localized electric field enhancement. I study the effect of interparticle distance over a wide range on their optical properties. Hedgehog particles, composed of a polystyrene core with ZnO spikes, possess special wettability that makes them dispersed in both hydrophilic and hydrophobic solvents. I reveal their optical properties that are very insensitive to spike geometry and environment. The findings presented in this dissertation bring deeper and more detailed understanding to the optical properties and ultrafast dynamics for such nanostructures. Advisors/Committee Members: Link, Stephan (advisor).

Subjects/Keywords: Plasmonic nanostructures; sing-particle spectroscopy; ultrafast dynacmis

10 more images…

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APA (6^th Edition):

Su, M. (2018). Optical Properties and Ultrafast Electron Dynamics in Gold, Aluminum and Hybrid Nanomaterials. (Doctoral Dissertation). Rice University. Retrieved from http://hdl.handle.net/1911/105844

Chicago Manual of Style (16^th Edition):

Su, Man-Nung. “Optical Properties and Ultrafast Electron Dynamics in Gold, Aluminum and Hybrid Nanomaterials.” 2018. Doctoral Dissertation, Rice University. Accessed April 12, 2021. http://hdl.handle.net/1911/105844.

MLA Handbook (7^th Edition):

Su, Man-Nung. “Optical Properties and Ultrafast Electron Dynamics in Gold, Aluminum and Hybrid Nanomaterials.” 2018. Web. 12 Apr 2021.

Vancouver:

Su M. Optical Properties and Ultrafast Electron Dynamics in Gold, Aluminum and Hybrid Nanomaterials. [Internet] [Doctoral dissertation]. Rice University; 2018. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/1911/105844.

Council of Science Editors:

Su M. Optical Properties and Ultrafast Electron Dynamics in Gold, Aluminum and Hybrid Nanomaterials. [Doctoral Dissertation]. Rice University; 2018. Available from: http://hdl.handle.net/1911/105844

Victoria University of Wellington

17. Pugliese, Silvina. Ultrafast Spectroscopy for Printable Photovoltaics.

Degree: 2020, Victoria University of Wellington

URL: http://hdl.handle.net/10063/9135

► The development of efficient and low cost photovoltaic technologies is key to a more sustainable energy pathway for future generations. Research efforts aimed at improving… (more)

▼ The development of efficient and low cost photovoltaic technologies is key to a more sustainable energy pathway for future generations. Research efforts aimed at improving the performance of organic photovoltaic (OPV) materials have resulted in a continuous growth in power conversion efficiency (PCE) over time, with a recent maximum PCE value of 18.22% in a single bulk heterojunction device. However, further improved efficiency, stability and cost reduction are required in order for OPVs to succeed in the market. To produce better performing OPV devices in a rational way, it is necessary to understand the relationships between material properties (e.g. energy levels, recombination rates, charge carrier mobilities) and the photovoltaic parameters. This requires combining different fundamental techniques, such as spectroscopic, electrical and structural studies of the materials. In this thesis work we contribute to the understanding of the mechanisms of charge photo-current generation in OPV layers by using transient absorption spectroscopy (TAS) to directly measure the fate of the photo-excited species created upon light absorption. In particular, we contribute to the understanding of the dynamical properties of tightly bound, interfacial charge-transfer (CT) states at the donor:acceptor heterojunction. We disentangle the contributions from individual transient species to the overall TAS signal via the soft-modelling algorithm known as Multivariate Curve Resolution by Alternating Least Squares (MCR-ALS), and we use simple kinetic models to retrieve associated kinetic rates. Our first study explores the photo-physics of a family of polymers derived from the low-band-gap alternating copolymer PTBT where the sulphur atom in the thiadiazole unit was substituted with oxygen or selenium. The literature shows that replacing a single atom in the donor or acceptor unit of a polymer donor can cause large changes in the photovoltaic parameters, which cannot be explained considering only the variations in the optical band-gap. Opposite results have been reported on systems where a sulfur atom is replaced by selenium, and spectroscopic studies were lacking. Our TAS results on PTBO and PTBSe systems explain the superior photovoltaic performance of the original sulfur-containing variant PTBT, highlighting the low tolerance of these materials to backbone substitutions. In both PTBO and PTBSe systems, we identify strong recombination of geminate CT pairs as the major limiting factor of the Jsc and FF photovoltaic parameters. This is attributed to unfavourable electronic and conformational properties at the donor:acceptor interface. In the particular case of PTBSe:PC61BM, the recombination pathway of CT states with triplet character into the triplet exciton manifold is facilitated by the heavy atom effect, in addition to a highly intermixed morphology. Our second study comprises the spectroscopic comparison between fullerene and nonfullerene (NFA) OPV layers. The PCE of OPV devices was reaching a plateau in past years, which was… Advisors/Committee Members: Hodgkiss, Justin.

Subjects/Keywords: Organic photovoltaics; Printable photovoltaics; Ultrafast laser spectroscopy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Pugliese, S. (2020). Ultrafast Spectroscopy for Printable Photovoltaics. (Doctoral Dissertation). Victoria University of Wellington. Retrieved from http://hdl.handle.net/10063/9135

Chicago Manual of Style (16^th Edition):

Pugliese, Silvina. “Ultrafast Spectroscopy for Printable Photovoltaics.” 2020. Doctoral Dissertation, Victoria University of Wellington. Accessed April 12, 2021. http://hdl.handle.net/10063/9135.

MLA Handbook (7^th Edition):

Pugliese, Silvina. “Ultrafast Spectroscopy for Printable Photovoltaics.” 2020. Web. 12 Apr 2021.

Vancouver:

Pugliese S. Ultrafast Spectroscopy for Printable Photovoltaics. [Internet] [Doctoral dissertation]. Victoria University of Wellington; 2020. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/10063/9135.

Council of Science Editors:

Pugliese S. Ultrafast Spectroscopy for Printable Photovoltaics. [Doctoral Dissertation]. Victoria University of Wellington; 2020. Available from: http://hdl.handle.net/10063/9135

University of Melbourne

18. Zeng, Peng. Ultrafast spectroscopy of nanostructures.

Degree: 2017, University of Melbourne

URL: http://hdl.handle.net/11343/212274

► This thesis presents studies of ultrafast laser spectroscopy of semiconductor and gold nanostructures, aiming to advance our understanding of, and consequently control, photoinduced charge carrier… (more)

▼ This thesis presents studies of ultrafast laser spectroscopy of semiconductor and gold nanostructures, aiming to advance our understanding of, and consequently control, photoinduced charge carrier dynamics in nanostructures to further improve their performance in practical applications. Artificial nanostructures have drawn significant attention in applications such as optoelectronic devices, photo-catalysts, and solar cells. Compared to bulk materials, nanostructures provide unique optical properties, which more importantly can be directly and easily tailored through changing size or shapes of the structures, during their synthesis procedures. Photoinduced charge carrier dynamics in the nanostructures play an important role in the photon conversion processes. However, in contrast to the fast development of nanostructure-based devices, the mechanisms of these processes are still being experimentally unravelled. In this study, a range of ultrafast optical spectroscopy methods have been applied to investigate the carrier dynamics, with a focus on the electron transfer (ET) process. Semiconductor nanoparticles, or quantum dots (QDs), of core/shell heterostructures are promising for their good photostability and high photoluminescence quantum yields. The ET dynamics from the 1S_e electron state to adsorbed methyl viologen electron acceptors, in CdSe/CdS and CdSe/CdS/ZnS QDs, were studied using femtosecond transient absorption and time-resolved photoluminescence spectroscopy. By changing shell thickness or alloying the shell interface, significant modulation of the ET dynamics was observed. In CdSe/CdS QDs, the 1S_e ET dynamics exhibited a hole-coupled effect, which is ascribed to the Auger-assisted ET process. In CdSe/CdS/ZnS QDs, the formation of alloyed shell interfaces at elevated shelling temperatures reduced the shell potential barrier, leading to an observed greater ET rate. Photoinduced ET processes from gold nanorod and nanowire structures to TiO₂ were also investigated, using a visible pump-NIR probe transient absorption spectroscopy method. Partially embedded Au nanorods on a TiO₂ layer exhibited an enhanced but directional ET process. An Au nanowire grating supported on a TiO₂ layer structure underwent the plasmon-waveguide hybridisation mechanism. The ET dynamics from the split states showed a dependence on the light-matter coupling effect that can be varied with the Au grating period. In summary, this thesis shows the great ability of ultrafast optical spectroscopy to reveal photoinduced processes in nanostructures. Results indicate ways for rational design of nanostructure-based devices. A greater understanding in underlying physics leads to better control of the performance of these nano-systems in potential practical applications.

Subjects/Keywords: ultrafast spectroscopy; nanostructures; quantum dots; plasmon

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APA (6^th Edition):

Zeng, P. (2017). Ultrafast spectroscopy of nanostructures. (Doctoral Dissertation). University of Melbourne. Retrieved from http://hdl.handle.net/11343/212274

Chicago Manual of Style (16^th Edition):

Zeng, Peng. “Ultrafast spectroscopy of nanostructures.” 2017. Doctoral Dissertation, University of Melbourne. Accessed April 12, 2021. http://hdl.handle.net/11343/212274.

MLA Handbook (7^th Edition):

Zeng, Peng. “Ultrafast spectroscopy of nanostructures.” 2017. Web. 12 Apr 2021.

Vancouver:

Zeng P. Ultrafast spectroscopy of nanostructures. [Internet] [Doctoral dissertation]. University of Melbourne; 2017. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/11343/212274.

Council of Science Editors:

Zeng P. Ultrafast spectroscopy of nanostructures. [Doctoral Dissertation]. University of Melbourne; 2017. Available from: http://hdl.handle.net/11343/212274

University of St. Andrews

19. Blaszczyk, Oskar. Measuring and controlling exciton diffusion, charge generation and charge extraction in organic and hybrid semiconductors for photovoltaic applications .

Degree: 2020, University of St. Andrews

URL: http://hdl.handle.net/10023/19950

► The growing demand for energy and the need for renewables as well as the advent of the internet of things increase the demand for more… (more)

▼ The growing demand for energy and the need for renewables as well as the advent of the internet of things increase the demand for more versatile, efficient, cheap and environmentally friendly solar cells based on organic and hybrid semiconductors. Understanding and controlling the underlying processes that govern exciton diffusion, charge generation, charge extraction and domain size is of vital importance to the efficiency, stability and scalability of these devices. This thesis examines in detail the exciton and charge carrier behaviour in, and the characteristics of new materials for organic and hybrid solar cell applications. A particular focus is put on measuring, understanding and controlling hole extraction from 𝐶𝐻₃𝑁𝐻₃𝑃𝑏𝐼₃ to hole extracting layers and overcoming the trade-off between exciton harvesting and charge extraction in small molecule bulk heterojunction organic solar cells. The main method used for this investigation was ultrafast timeresolved spectroscopy, specifically ultrafast optical transient absorption and ultrafast time-resolved fluorescence decay with a streak camera. A study of hole extraction from 𝐶𝐻₃𝑁𝐻₃𝑃𝑏𝐼₃ was carried out for two different hole extracting layers, the standard PEDOT:PSS polymer used in the inverted p-i-n perovskite solar cells and a new nanoparticle NiO low temperature solution processed thin film. The two extraction layers and the 𝐶𝐻₃𝑁𝐻₃𝑃𝑏𝐼₃ perovskite active layer were first characterized using optical and physical methods such as UV-Vis spectroscopy and atomic force microscopy as well as air photoemission spectroscopy to confirm that the same perovskite was grown on top of both PEDOT:PSS and NiO and to investigate energy level alignment. A new method based on the ultrafast photoluminescence surface quenching experiment was developed and introduced which allows for the separation of bulk and interfacial effects on charge extraction from thin films by illuminating the samples from opposite sides. This new method was used to compare hole extraction from 𝐶𝐻₃𝑁𝐻₃𝑃𝑏𝐼₃ to NiO and PEDOT:PSS. It was found that NiO shows faster hole extraction from the 300 nm thick perovskite film than PEDOT:PSS on the time scale of 300 ps, which is independent of charge carrier density in the region of 10¹⁶-10¹⁷ cm⁻³. The interface with PEDOT:PSS was found to severely limit charge extraction rate at charge densities exceeding 10¹⁶ cm⁻³. Furthermore, the transfer rate was found to decrease with time and to be dependent on charge density in the region 10¹⁶-10¹⁷ cm⁻³ which we interpreted as charge accumulation. These findings were confirmed by transient absorption spectroscopy. Hole diffusion coefficient 𝐷 = 2.2 cm²/s ± 0.4 cm²/s and quenching rate k=3.6 × 10⁵ m/s ±0.2 m/s were determined in the perovskite film that were independent of charge density. This indicates a band-like hole transport regime, not observed for solution processed CH₃NH₃PbI₃ films before. Our findings stress the importance of interface optimization in devices based on perovskite… Advisors/Committee Members: Samuel, Ifor D. W (advisor).

Subjects/Keywords: Perovskite; Organic semiconductor; Photovoltaics; Ultrafast spectroscopy

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APA (6^th Edition):

Blaszczyk, O. (2020). Measuring and controlling exciton diffusion, charge generation and charge extraction in organic and hybrid semiconductors for photovoltaic applications . (Thesis). University of St. Andrews. Retrieved from http://hdl.handle.net/10023/19950

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Blaszczyk, Oskar. “Measuring and controlling exciton diffusion, charge generation and charge extraction in organic and hybrid semiconductors for photovoltaic applications .” 2020. Thesis, University of St. Andrews. Accessed April 12, 2021. http://hdl.handle.net/10023/19950.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Blaszczyk, Oskar. “Measuring and controlling exciton diffusion, charge generation and charge extraction in organic and hybrid semiconductors for photovoltaic applications .” 2020. Web. 12 Apr 2021.

Vancouver:

Blaszczyk O. Measuring and controlling exciton diffusion, charge generation and charge extraction in organic and hybrid semiconductors for photovoltaic applications . [Internet] [Thesis]. University of St. Andrews; 2020. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/10023/19950.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Blaszczyk O. Measuring and controlling exciton diffusion, charge generation and charge extraction in organic and hybrid semiconductors for photovoltaic applications . [Thesis]. University of St. Andrews; 2020. Available from: http://hdl.handle.net/10023/19950

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of California – Berkeley

20. Hoffman, David Paul. Molecular Choreography of Isomerization and Electron Transfer Using One and Two Dimensional Femtosecond Stimulated Raman Spectroscopy.

Degree: Chemistry, 2014, University of California – Berkeley

URL: http://www.escholarship.org/uc/item/61x7x2r8

► Chemical reactions are defined by the change in the relative positions and bonding of nuclei in molecules. I have used femtosecond stimulated Raman spectroscopy (FSRS)… (more)

▼ Chemical reactions are defined by the change in the relative positions and bonding of nuclei in molecules. I have used femtosecond stimulated Raman spectroscopy (FSRS) to probe these transformations with structural specificity and high time precision revealing the mechanisms of two important classes of reactions; isomerization about an N=N bond and interfacial/intermolecular electron transfer.Isomerization about a double bond is one of the simplest, yet most important, photochemical reactions. In contrast to carbon double bonds, nitrogen double bonds can react via two possible mechanisms; rotation or inversion. To determine which pathway is predominant, I studied an azobenzene derivative using both FSRS and impulsive stimulated Raman spectroscopy (ISRS). The FSRS experiments demonstrated that the photochemical reaction occurs concomitantly with the 700 fs non-radiative decay of the excited state; because no major change in N=N stretching frequency was measured, I surmised that the reaction proceeds through an inversion pathway. My subsequent ISRS experiments confirmed this hypothesis; I observed a highly displaced, low frequency, inversion-like mode, indicating that initial movement out of the Franck-Condon region proceeds along an inversion coordinate. To probe which nuclear motions facilitate electron transfer and charge recombination, I used FSRS and the newly developed 2D-FSRS techniques to study two model systems, triphenylamine dyes bound to TiO₂ nanoparticles and a molecular charge transfer (CT) dimer. In the dye-nanoparticle system I discovered that charge separation persists much longer (> 100 ps) than previously thought by using the juxtaposition of the FSRS and transient absorption data to separate the dynamics of the dye from that of the injected electron. Additionally, I discovered that dye constructs with an added vinyl group were susceptible to quenching via isomerization. The CT dimer offered an opportunity to study a system in which charge recombination occurred on a shorter timescale (~10 ps). Here I found that impulsively excited coherent nuclear motion in the excited state survived for more than 5 ps. These long lived coherences enabled the performance of 2D-FSRS to identify the coupling and tuning modes of the conical intersection that connects the charge transfer excited state with the neutral ground state and therefore the nuclear motions responsible for charge recombination. Furthermore, these data demonstrate that the photochemical reactivity is not mediated by phase-space randomization but rather by specific, coherent, nuclear trajectories.In this thesis I have demonstrated the power and utility of FSRS in probing condensed phase chemical reaction dynamics and provided a glimpse of the capabilities of 2D-FSRS. In general, 2D-FSRS provides a direct measure of the anharmonic coupling that controls reactivity. Looking forward, higher time resolution (broader band) 2D-FSRS will open up a whole new approach for characterizing transition states and energy transfer…

Subjects/Keywords: Chemistry; Physical chemistry; Electron transfer; Isomerization; Raman Spectroscopy; Ultrafast Spectroscopy

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APA (6^th Edition):

Hoffman, D. P. (2014). Molecular Choreography of Isomerization and Electron Transfer Using One and Two Dimensional Femtosecond Stimulated Raman Spectroscopy. (Thesis). University of California – Berkeley. Retrieved from http://www.escholarship.org/uc/item/61x7x2r8

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Hoffman, David Paul. “Molecular Choreography of Isomerization and Electron Transfer Using One and Two Dimensional Femtosecond Stimulated Raman Spectroscopy.” 2014. Thesis, University of California – Berkeley. Accessed April 12, 2021. http://www.escholarship.org/uc/item/61x7x2r8.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Hoffman, David Paul. “Molecular Choreography of Isomerization and Electron Transfer Using One and Two Dimensional Femtosecond Stimulated Raman Spectroscopy.” 2014. Web. 12 Apr 2021.

Vancouver:

Hoffman DP. Molecular Choreography of Isomerization and Electron Transfer Using One and Two Dimensional Femtosecond Stimulated Raman Spectroscopy. [Internet] [Thesis]. University of California – Berkeley; 2014. [cited 2021 Apr 12]. Available from: http://www.escholarship.org/uc/item/61x7x2r8.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Hoffman DP. Molecular Choreography of Isomerization and Electron Transfer Using One and Two Dimensional Femtosecond Stimulated Raman Spectroscopy. [Thesis]. University of California – Berkeley; 2014. Available from: http://www.escholarship.org/uc/item/61x7x2r8

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Vanderbilt University

21. Garnett, Joy Carleen. The Evolution of Surface Symmetry in Femtosecond Laser-Induced Transient States of Matter.

Degree: PhD, Interdisciplinary Materials Science, 2017, Vanderbilt University

URL: http://hdl.handle.net/1803/11538

► Gallium arsenide and other III-V materials are well known for their excellent optical and electronic properties and have led to the development of high-performance optoelectronics.… (more)

Subjects/Keywords: ultrafast spectroscopy; femtosecond; second harmonic generation; nonlinear optics; nonlinear spectroscopy

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APA (6^th Edition):

Garnett, J. C. (2017). The Evolution of Surface Symmetry in Femtosecond Laser-Induced Transient States of Matter. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/11538

Chicago Manual of Style (16^th Edition):

Garnett, Joy Carleen. “The Evolution of Surface Symmetry in Femtosecond Laser-Induced Transient States of Matter.” 2017. Doctoral Dissertation, Vanderbilt University. Accessed April 12, 2021. http://hdl.handle.net/1803/11538.

MLA Handbook (7^th Edition):

Garnett, Joy Carleen. “The Evolution of Surface Symmetry in Femtosecond Laser-Induced Transient States of Matter.” 2017. Web. 12 Apr 2021.

Vancouver:

Garnett JC. The Evolution of Surface Symmetry in Femtosecond Laser-Induced Transient States of Matter. [Internet] [Doctoral dissertation]. Vanderbilt University; 2017. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/1803/11538.

Council of Science Editors:

Garnett JC. The Evolution of Surface Symmetry in Femtosecond Laser-Induced Transient States of Matter. [Doctoral Dissertation]. Vanderbilt University; 2017. Available from: http://hdl.handle.net/1803/11538

Texas A&M University

22. Shen, Yujie. Towards Fast Coherent Anti-Stokes Raman Scattering Microspectroscopy.

Degree: PhD, Physics, 2018, Texas A&M University

URL: http://hdl.handle.net/1969.1/174640

► Coherent anti-Stokes Raman scattering (CARS) microspectroscopy is a nonlinear spectroscopy and imaging technique that probes the vibrational and rotational modes of the molecule, enabling chemical-selective… (more)

▼ Coherent anti-Stokes Raman scattering (CARS) microspectroscopy is a nonlinear spectroscopy and imaging technique that probes the vibrational and rotational modes of the molecule, enabling chemical-selective microscopy. Over the past years, CARS has found applications in a wide range of fields such as tumor imaging, gas sensing, and flow cytometry. More recently, commercial components and even a microscopic solution dedicated to CARS has become available. This research is devoted to the development of a high-speed, high-sensitivity CARS microspectroscopy system for chemical and biomedical analysis. We started with an easy-to-implement CARS scheme based on ultrafast pulse shaping of single laser beam. We demonstrated an improved setup that achieved higher epi-detection efficiency as compared to earlier experiment, and allowed low-wavenumber Raman band detection below 100 cm. We further simplified our setup by adopting a folded pulse-shaper design, and incorporated the femtosecond adaptive spectroscopic technique (FAST) developed earlier in the group to achieve versatile single-beam CARS detection with significant nonresonant background suppression. Finally, through utilizing the phase information contained in the signal, we devised and implemented an upgraded system by adopting heterodyne detection in the single-beam CARS setup to achieve high speed spectral detection with background suppression. We have also combined spectral detection and pulse shaping in the setup so as to achieve a one-box-solution for CARS measurement. To further extend the Raman detection range, it is necessary to incorporate means of wavelength extension to achieve broadband excitation. We studied the supercontinuum (SC) generation in large mode area photonic crystal fiber pumped by an industrial picosecond laser. Such an extension unit allowed a simultaneous Raman excitation bandwidth of over 3000 cm?1. We built a multiplex CARS system based on this SC source, and demonstrated its applicability through imaging standard samples. We further constructed a laser-scanning CARS microscope that can provide high spectral resolution and acquisition speed, and showed its capability in 3-dimensional scanning CARS microscopy. In order to boost CARS imaging speed, we also experimented with the wide-field CARS scheme, in which CARS excitation was performed over a large area simultaneously. Using the high-power SC source, we combined the wide-field CARS with multiplex CARS excitation scheme, such that a broad range of Raman modes over a significant spatial region were excited, and CARS image was obtained by applying a corresponding filter. We showed chemical-selective imaging using standard polymer microsphere samples, and demonstrated video-rate CARS microscopy using this setup. Advisors/Committee Members: Scully, Marlan O (advisor), Sokolov, Alexei V (advisor), Fry, Edward S (committee member), Hemmer, Philip (committee member), Zheltikov, Aleksei M (committee member), Yakovlev, Vladislav V (committee member).

Subjects/Keywords: Nonlinear spectroscopy; Raman spectroscopy; Ultrafast laser technology; Microscopy; Nonlinear fiber optics

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APA (6^th Edition):

Shen, Y. (2018). Towards Fast Coherent Anti-Stokes Raman Scattering Microspectroscopy. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/174640

Chicago Manual of Style (16^th Edition):

Shen, Yujie. “Towards Fast Coherent Anti-Stokes Raman Scattering Microspectroscopy.” 2018. Doctoral Dissertation, Texas A&M University. Accessed April 12, 2021. http://hdl.handle.net/1969.1/174640.

MLA Handbook (7^th Edition):

Shen, Yujie. “Towards Fast Coherent Anti-Stokes Raman Scattering Microspectroscopy.” 2018. Web. 12 Apr 2021.

Vancouver:

Shen Y. Towards Fast Coherent Anti-Stokes Raman Scattering Microspectroscopy. [Internet] [Doctoral dissertation]. Texas A&M University; 2018. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/1969.1/174640.

Council of Science Editors:

Shen Y. Towards Fast Coherent Anti-Stokes Raman Scattering Microspectroscopy. [Doctoral Dissertation]. Texas A&M University; 2018. Available from: http://hdl.handle.net/1969.1/174640

Penn State University

23. Rimshaw, Adam. DEVELOPMENT OF VISIBLE, NEAR-INFRARED, AND MID-INFRARED TRANSIENT ABSORPTION SPECTROSCOPY ON A FEMTOSECOND TO MILLISECOND TIMESCALE AND ITS APPLICABILITY TO ORGANIC ELECTRONIC MATERIALS.

Degree: 2016, Penn State University

URL: https://submit-etda.libraries.psu.edu/catalog/3t945q772

► Nanosecond transient absorption instruments capable of 10-5 sensitivity were developed for visible, near-infrared, and mid-infrared spectral regions. These instruments were developed around new advances in… (more)

▼ Nanosecond transient absorption instruments capable of 10-5 sensitivity were developed for visible, near-infrared, and mid-infrared spectral regions. These instruments were developed around new advances in analogue to digital (ADC) conversion called flexible resolution. Unlike the traditional ADC architecture, which interleaves multiple 8-bit ADCs to achieve higher resolution, the digitizers used within this manuscript allows multiple high-resolution ADCs to be applied to the input channels in different time-interleaved and parallel combinations to boost either the sampling rate or the resolution. The result is instrumentation capable of changing resolution (8-14 bit), which helps to increase the signal-to-noise ratio by more than an order of magnitude. For each instrument, the spectral and temporal range is explored with an emphasis on the sensitivity and collection time. The detection limit of both nanosecond instruments was calculated to be 10-5 O.D. Example materials were studied on both nanosecond instruments to show their capability in real-world applications with systems such as P3HT:PCBM, CN-MEH-PPV and TIPS-pentacene. The mid-IR instrument provided some of most sensitivity spectra ever recorded in the mid-IR, such as alkyne stretches measuring < 100 μO.D. in TIPS-pentacene films on a nanosecond timescale. The ability to record such data within a reasonable time frame makes possible for significantly lower energy densities to be used in studying organic electronic materials. Our ultrafast laser system was expanded to perform visible pump―visible pump spectroscopy and our preexisting visible pump―mid-IR pump was redesigned with new technologies such as remote connectivity. All of the instrument’s programming was redone using MATLAB―streamlining our data collection and analysis. Important advances were made in terms of data acquisition time and statistical filtering using the new software as well. The redesigned system allowed us to start exploring perylene diimide solutions for unique vibrational modes due to excimer formation. Lastly, these advances have opened the door to developing a new kind of ultrafast technique termed pump-push-probe, which allows for photophysics to be studied on functioning organic electronic devices. Advisors/Committee Members: John B Asbury, Dissertation Advisor/Co-Advisor, John B Asbury, Committee Chair/Co-Chair, Mark Maroncelli, Committee Member, Benjamin James Lear, Committee Member, Enrique Daniel Gomez, Outside Member.

Subjects/Keywords: Ultrafast Spectroscopy; Nanosecond Spectroscopy; Organic Photovoltaics; Organic Solar Cells

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APA (6^th Edition):

Rimshaw, A. (2016). DEVELOPMENT OF VISIBLE, NEAR-INFRARED, AND MID-INFRARED TRANSIENT ABSORPTION SPECTROSCOPY ON A FEMTOSECOND TO MILLISECOND TIMESCALE AND ITS APPLICABILITY TO ORGANIC ELECTRONIC MATERIALS. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/3t945q772

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Rimshaw, Adam. “DEVELOPMENT OF VISIBLE, NEAR-INFRARED, AND MID-INFRARED TRANSIENT ABSORPTION SPECTROSCOPY ON A FEMTOSECOND TO MILLISECOND TIMESCALE AND ITS APPLICABILITY TO ORGANIC ELECTRONIC MATERIALS.” 2016. Thesis, Penn State University. Accessed April 12, 2021. https://submit-etda.libraries.psu.edu/catalog/3t945q772.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Rimshaw, Adam. “DEVELOPMENT OF VISIBLE, NEAR-INFRARED, AND MID-INFRARED TRANSIENT ABSORPTION SPECTROSCOPY ON A FEMTOSECOND TO MILLISECOND TIMESCALE AND ITS APPLICABILITY TO ORGANIC ELECTRONIC MATERIALS.” 2016. Web. 12 Apr 2021.

Vancouver:

Rimshaw A. DEVELOPMENT OF VISIBLE, NEAR-INFRARED, AND MID-INFRARED TRANSIENT ABSORPTION SPECTROSCOPY ON A FEMTOSECOND TO MILLISECOND TIMESCALE AND ITS APPLICABILITY TO ORGANIC ELECTRONIC MATERIALS. [Internet] [Thesis]. Penn State University; 2016. [cited 2021 Apr 12]. Available from: https://submit-etda.libraries.psu.edu/catalog/3t945q772.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Rimshaw A. DEVELOPMENT OF VISIBLE, NEAR-INFRARED, AND MID-INFRARED TRANSIENT ABSORPTION SPECTROSCOPY ON A FEMTOSECOND TO MILLISECOND TIMESCALE AND ITS APPLICABILITY TO ORGANIC ELECTRONIC MATERIALS. [Thesis]. Penn State University; 2016. Available from: https://submit-etda.libraries.psu.edu/catalog/3t945q772

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Edinburgh

24. Johansson, Olof Johan. Angle-resolved femtosecond photoelectron spectroscopy of fullerenes.

Degree: PhD, 2011, University of Edinburgh

URL: http://hdl.handle.net/1842/5038

► An experimental apparatus has been constructed to investigate ionisation mechanisms of complex molecules and nanoparticles after femtosecond and/or picosecond laser excitation. The photoproducts are detected… (more)

▼ An experimental apparatus has been constructed to investigate ionisation mechanisms of complex molecules and nanoparticles after femtosecond and/or picosecond laser excitation. The photoproducts are detected by time-of-flight mass spectrometry and velocity-map imaging (VMI) photoelectron spectroscopy. Test measurements on C60 and Xe have successfully reproduced previously published work indicating that the setup is working in a satisfactory manner. New detailed investigations of mass spectra and angle resolved photoelectron spectra (PES) have been carried out as a function of laser intensity, wavelength and pulse duration for C60 and C70, providing new insights into the electronic structure and ionisation mechanisms of these molecules. For 400 nm, 130 fs laser excitation, an isotropic contribution from thermally emitted electrons is found. A series of peaks are seen superimposed on the thermal background with binding energies in agreement with the recently discovered superatom molecular orbitals (SAMOs) of C60 [Feng et.al. Science 320 (2008) p. 359]. Furthermore, the angular dependence of the peak in the PES corresponding to the s-SAMO is in agreement with this assignment. To confirm the assignment of the other observed peaks it is concluded that the measured photoelectron angular distributions (PADs) need to be compared to calculated angular distributions. Measurements have also been made with the same wavelength but with a pulse duration of about 5 ps. Mass spectra, PES and PADs for these measurements show that the main ionisation mechanism for these laser conditions is delayed (thermionic) ionisation. For 800 nm, 130 and 180 fs laser excitation, thermally emitted electrons are observed. In contrast to the 400 nm measurements, the PADs show an asymmetry with higher apparent temperatures along the laser polarisation direction. Measurements were also made for longer pulse durations (1.0 – 3.8 ps). For pulse durations above 1 ps the asymmetry is gradually reduced while the delayed ionisation component in the mass spectrum increases with increasing pulse duration. The asymmetry is compared to calculations made assuming a field-assisted thermal electron emission. Similarly to the 400 nm experiments, a series of peaks are seen superimposed on the thermal background. PADs are presented for these peaks. PADs for peaks with the same binding energy as peaks seen in the 400 nm experiments follow the same trend. Isotropic PADs after ns laser excitation are also presented confirming delayed ionisation for these pulse durations.

Subjects/Keywords: 535; physical chemistry; fullerenes; photoelectron spectroscopy; ultrafast spectroscopy

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APA (6^th Edition):

Johansson, O. J. (2011). Angle-resolved femtosecond photoelectron spectroscopy of fullerenes. (Doctoral Dissertation). University of Edinburgh. Retrieved from http://hdl.handle.net/1842/5038

Chicago Manual of Style (16^th Edition):

Johansson, Olof Johan. “Angle-resolved femtosecond photoelectron spectroscopy of fullerenes.” 2011. Doctoral Dissertation, University of Edinburgh. Accessed April 12, 2021. http://hdl.handle.net/1842/5038.

MLA Handbook (7^th Edition):

Johansson, Olof Johan. “Angle-resolved femtosecond photoelectron spectroscopy of fullerenes.” 2011. Web. 12 Apr 2021.

Vancouver:

Johansson OJ. Angle-resolved femtosecond photoelectron spectroscopy of fullerenes. [Internet] [Doctoral dissertation]. University of Edinburgh; 2011. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/1842/5038.

Council of Science Editors:

Johansson OJ. Angle-resolved femtosecond photoelectron spectroscopy of fullerenes. [Doctoral Dissertation]. University of Edinburgh; 2011. Available from: http://hdl.handle.net/1842/5038

Florida International University

25. Titze, Michael. Coherent and Incoherent Dynamics of Quasiparticles in Monolayer Molybdenum Diselenide.

Degree: PhD, Physics, 2019, Florida International University

URL: https://digitalcommons.fiu.edu/etd/4033 ; 10.25148/etd.FIDC007650 ; FIDC007650

► Monolayer Materials, especially single-layer graphite, called graphene, as the first synthesized and most prominent representative, have attracted significant research interest since its discovery in… (more)

▼ Monolayer Materials, especially single-layer graphite, called graphene, as the first synthesized and most prominent representative, have attracted significant research interest since its discovery in 2004. The efforts were rewarded with a Nobel prize in 2010 for the discovery of graphene, the same year in which the first monolayer transition metal dichalcogenide (ML-TMD) was found to have a direct bandgap. In contrast to graphene ML-TMDs have a direct bandgap in the visible or near-infrared spectral range, making them ideally suited for optoelectronic device applications. Explicit inversion symmetry breaking of the unit cell in ML-TMDs furthermore leads to a new interesting property, called valley pseudo-spin. Electrons excited within one valley are restricted to this valley due to momentum trapping. Investigating the valley pseudo-spin dynamics is of importance for both understanding of the fundamental physics as well as device applications since the valley pseudo-spin is a potential information carrier and has potential use for information storage or computing application. Additionally, the confinement to two dimensions leads to enhanced Coulomb interaction and increased dielectric screening between electron and hole. Interestingly, the two-dimensional screening effects were already studied before the first two-dimensional materials were synthesized on quasi-two-dimensional systems. The screening of the Coulomb interaction in turn leads to a significantly increased binding energy between electron and hole, such that the bound electron-hole state, so-called exciton, is stable up to room temperature and above. The same reasoning leads to an enhanced stability of charged excitons, so-called trions, which are the main focus of this dissertation. The optical response of ML-TMDs is therefore completely dominated by excitons and trions, requiring an in-depth understanding of these quasiparticles for device performance optimization. Time-resolved techniques can offer rich information compared to steady-state measurements. While steady-state measurements can resolve things such as the bandgap of a semiconductor or the fact that valley spin exists, time-resolved techniques allow the access of transients and reveal the lifetime of unstable or metastable states, which may be invisible in steady-state measurements. Coherent techniques are known for their ability of probing many-body effects and microscopic inhomogeneity. The technique used to investigate the coherent trion dynamics in this dissertation is two-dimensional coherent spectroscopy, a nonlinear coherent technique, that resolves the signal as a function of two time delays. Using two-dimensional spectroscopy, it is possible to measure the homogeneous linewidth, which is related to the coherence time, even in a strongly inhomogeneously broadened system. The measurement of the coherence time marks the first step in evaluating a material for possible quantum computation applications. Advisors/Committee Members: Hebin Li, Bernard Gerstman, Raphael Raptis, Yifu Zhu.

Subjects/Keywords: ultrafast spectroscopy; monolayer semiconductors; coherent spectroscopy; Physical Sciences and Mathematics; Physics

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APA (6^th Edition):

Titze, M. (2019). Coherent and Incoherent Dynamics of Quasiparticles in Monolayer Molybdenum Diselenide. (Doctoral Dissertation). Florida International University. Retrieved from https://digitalcommons.fiu.edu/etd/4033 ; 10.25148/etd.FIDC007650 ; FIDC007650

Chicago Manual of Style (16^th Edition):

Titze, Michael. “Coherent and Incoherent Dynamics of Quasiparticles in Monolayer Molybdenum Diselenide.” 2019. Doctoral Dissertation, Florida International University. Accessed April 12, 2021. https://digitalcommons.fiu.edu/etd/4033 ; 10.25148/etd.FIDC007650 ; FIDC007650.

MLA Handbook (7^th Edition):

Titze, Michael. “Coherent and Incoherent Dynamics of Quasiparticles in Monolayer Molybdenum Diselenide.” 2019. Web. 12 Apr 2021.

Vancouver:

Titze M. Coherent and Incoherent Dynamics of Quasiparticles in Monolayer Molybdenum Diselenide. [Internet] [Doctoral dissertation]. Florida International University; 2019. [cited 2021 Apr 12]. Available from: https://digitalcommons.fiu.edu/etd/4033 ; 10.25148/etd.FIDC007650 ; FIDC007650.

Council of Science Editors:

Titze M. Coherent and Incoherent Dynamics of Quasiparticles in Monolayer Molybdenum Diselenide. [Doctoral Dissertation]. Florida International University; 2019. Available from: https://digitalcommons.fiu.edu/etd/4033 ; 10.25148/etd.FIDC007650 ; FIDC007650

University of Minnesota

26. Huber, Christopher. Studying Si-H Mode Sensitivity to Internal and External Perturbations through Vibrational Spectroscopy.

Degree: PhD, Chemistry, 2015, University of Minnesota

URL: http://hdl.handle.net/11299/175536

► Over the course of this thesis, I hope to display an understanding of how a vibrational mode's sensitivity is dictated by inter- and intramolecular structure… (more)

Subjects/Keywords: 2D-IR; Confined Dynamics; Infrared Spectroscopy; Silica Sol-Gel; Ultrafast Spectroscopy

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APA (6^th Edition):

Huber, C. (2015). Studying Si-H Mode Sensitivity to Internal and External Perturbations through Vibrational Spectroscopy. (Doctoral Dissertation). University of Minnesota. Retrieved from http://hdl.handle.net/11299/175536

Chicago Manual of Style (16^th Edition):

Huber, Christopher. “Studying Si-H Mode Sensitivity to Internal and External Perturbations through Vibrational Spectroscopy.” 2015. Doctoral Dissertation, University of Minnesota. Accessed April 12, 2021. http://hdl.handle.net/11299/175536.

MLA Handbook (7^th Edition):

Huber, Christopher. “Studying Si-H Mode Sensitivity to Internal and External Perturbations through Vibrational Spectroscopy.” 2015. Web. 12 Apr 2021.

Vancouver:

Huber C. Studying Si-H Mode Sensitivity to Internal and External Perturbations through Vibrational Spectroscopy. [Internet] [Doctoral dissertation]. University of Minnesota; 2015. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/11299/175536.

Council of Science Editors:

Huber C. Studying Si-H Mode Sensitivity to Internal and External Perturbations through Vibrational Spectroscopy. [Doctoral Dissertation]. University of Minnesota; 2015. Available from: http://hdl.handle.net/11299/175536

University of Texas – Austin

27. Hao, Kai, Ph. D. Quantum coherent dynamics of excitons and valley pseudospins in atomically thin semiconductors.

Degree: PhD, Physics, 2018, University of Texas – Austin

URL: http://hdl.handle.net/2152/68921

► Monolayer transition metal dichalcogenides (TMDCs) are new emerging van der Waals materials. Several TMDC materials go through with a transition from indirect to direct gap… (more)

▼ Monolayer transition metal dichalcogenides (TMDCs) are new emerging van der Waals materials. Several TMDC materials go through with a transition from indirect to direct gap semiconductors when reduced to monolayer thickness limit with emission in the visible to near-infrared range, making them attractive materials for optoelectronic applications. Their near-gap optical properties are dominant by excitons (bound electron-hole pairs), charged excitons (known as trions) or higher order bound states (e.g., neutral and charged biexcitons). In this dissertation, we explored the quantum coherent dynamics of exciton, trions and their associated valley index using a powerful ultrafast spectroscopy tool known as the two-dimensional coherent spectroscopy (2DCS). We investigated the underlying mechanisms that determined the valley coherence associated with excitons and trions. In monolayer TMDCs, there are two inequivalent K and K’ points in momentum space, where the band extrema are located and the excitons are formed. The excitonic states in the two valleys are selectively coupled to light with opposite helicity. This valley contrasting optical selection rules allow one to address and manipulate the valley index readily, a unique property and advantage of TMDC materials for valleytronic applications. The valley coherence can be quantitatively evaluated in polarization resolved zero-quantum 2D spectra. We found that the exciton valley coherence is limited by the electron-hole exchange interaction in the system. In contrast, for the charged exciton (trion) states, where the inter-valley scattering is suppressed, it is the intra-valley pure dephasing limits the inter-valley coherence time. These results provide the insight of valley coherence dynamics in monolayer TMDCs and suggest possible approaches to improve the valley coherence time. Next, we investigate the coherence coupling between excitons and trions created in one valley. The trions are charged quasiparticles which contribute to the charge transport directly. Thus, the coupling between exciton and trion states can significantly influent the interpretation of transport measurements. We demonstrate that these two types of quasiparticles are coherently coupled to each other by the observation of the quantum beating of the cross-diagonal peaks in one-quantum 2D spectra. The coherence time between them can be extracted by monitoring the amplitude decay of the beating signal. We found that the coherent coupling dephasing rate between the exciton and trion equals to the sum of the exciton and trion dephasing rate, indicating uncorrelated dephasing process for excitons and trions. At longer time scale, the phonon-assisted energy transfer couples the two states incoherently. Finally, we studied the higher order correlated states in monolayer TMDCs. We used polarization resolved 2DCS to reveal bounded inter-valley neutral biexcitons and charged biexcitons as new peaks which spectrally shifted in 2D spectra. The binding energies of these biexcitons are ∼20 and ∼5 meV… Advisors/Committee Members: Li, Elaine (advisor), MacDonald, Allan (committee member), Downer, Michael (committee member), Shih, Chih-Kang (committee member), Tutuc, Emanuel (committee member).

Subjects/Keywords: Semiconductor; Spectroscopy; Ultrafast spectroscopy; Exciton physics; Valley-pseudospin

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Hao, Kai, P. D. (2018). Quantum coherent dynamics of excitons and valley pseudospins in atomically thin semiconductors. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/68921

Chicago Manual of Style (16^th Edition):

Hao, Kai, Ph D. “Quantum coherent dynamics of excitons and valley pseudospins in atomically thin semiconductors.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed April 12, 2021. http://hdl.handle.net/2152/68921.

MLA Handbook (7^th Edition):

Hao, Kai, Ph D. “Quantum coherent dynamics of excitons and valley pseudospins in atomically thin semiconductors.” 2018. Web. 12 Apr 2021.

Vancouver:

Hao, Kai PD. Quantum coherent dynamics of excitons and valley pseudospins in atomically thin semiconductors. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/2152/68921.

Council of Science Editors:

Hao, Kai PD. Quantum coherent dynamics of excitons and valley pseudospins in atomically thin semiconductors. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://hdl.handle.net/2152/68921

University of Illinois – Urbana-Champaign

28. Gentle, Cecilia Marie. Internal atomic-scale structure and photothermal dynamics of heterostructured nanomaterials.

Degree: PhD, Chemistry, 2020, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/109323

► In this thesis we adopt a multimodal materials characterization approach to unravel the internal structure and the photoexcited electronic and geometric structural dynamics of Cd𝑥Zn1−𝑥Te/CdSe… (more)

▼ In this thesis we adopt a multimodal materials characterization approach to unravel the internal structure and the photoexcited electronic and geometric structural dynamics of Cd𝑥Zn1−𝑥Te/CdSe core/shell quantum dots (QDs). These QDs belong to a broader class of heterostructured II-VI semiconducting that are known for their applications in optoelectronics and biomedical imaging. The foundation of this thesis is the determination of the internal structure of II-VI core/shell quantum dots (CSQDs) using a combination of several characterization modes, with X-ray absorption spectroscopy (XAS) as a crucial element-specific technique. Through a combination of optical spectroscopy, electron microscopy, elemental analysis, and the global analysis of the extended X-ray absorption fine structure (EXAFS) spectrum, we show that the intended ZnTe/CdSe CSQDs, that are synthesized using a common one-pot synthesis procedure, are in actuality nanoparticles with an alloyed core and a patchy CdSe shell. Electronic structure calculations show that the CSQDs essentially behave as one-component QDs with a direct band gap. Cation exchange and the unintended reaction of molecular precursors prevent the formation of a sharp type-II ZnTe/CdSe interface with small lattice mismatch. Instead, the large interfacial strain between Cd𝑥Zn1−𝑥Te (𝑥 = 0.8) and pure-phase CdSe leads to the growth of islands on the QD surface. Our results corroborate the challenges associated with the synthesis of Zn/Cd chalcogenide type-II heterostructures due to facile ion exchange. This study is an example of how the assessment of heterogeneous nanomaterials on the basis of spectroscopy or size analysis alone is not always sufficient. While our XAS data were obtained at a large-scale synchrotron X-ray facility with specialized infrastructure and limited access, the advent of tunable high-brightness table-top X-ray sources will enable characterization studies on heterostructured photovoltaic and photocatalytic nanomaterials with much higher throughput and more experimental flexibility. We use density functional theory in combination with state-of-the art theoretical XAS codes to demonstrate the sensitivity of the X-ray absorption near-edge structure (XANES) to the local structure beyond the first coordination shell. In this way, we are able to corroborate the structural characterization of the alloyed Cd𝑥Zn1−𝑥Te (𝑥 = 0.8) core as determined by EXAFS analysis. This work underscores the power of XAS, in both experiment and simulation, for understanding the internal structure of heterogeneous nanoparticles. Ultrafast XAS is a powerful tool to unravel the electronic and geometric structures of photoexcited materials with femtosecond (fs)-nanosecond (ns) resolution. Using systematic DFT-based XAS simulations, we show that the time-resolved XANES spectra of nanoparticles at early time delays after photoexcitation (90 picoseconds, ps) are dominated by thermal effects, such as a 0.2% lattice expansion and disorder, while spectra at later times (2.5 ns) have clear… Advisors/Committee Members: van der Veen, Renske (advisor), van der Veen, Renske (Committee Chair), Shim, Moonsub (committee member), Vura-Weis, Josh (committee member), Murphy, Catherine J. (committee member).

Subjects/Keywords: Quantum dots; semiconductors; X-ray absorption spectroscopy; photothermal dynamics; ultrafast spectroscopy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Gentle, C. M. (2020). Internal atomic-scale structure and photothermal dynamics of heterostructured nanomaterials. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/109323

Chicago Manual of Style (16^th Edition):

Gentle, Cecilia Marie. “Internal atomic-scale structure and photothermal dynamics of heterostructured nanomaterials.” 2020. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed April 12, 2021. http://hdl.handle.net/2142/109323.

MLA Handbook (7^th Edition):

Gentle, Cecilia Marie. “Internal atomic-scale structure and photothermal dynamics of heterostructured nanomaterials.” 2020. Web. 12 Apr 2021.

Vancouver:

Gentle CM. Internal atomic-scale structure and photothermal dynamics of heterostructured nanomaterials. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2020. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/2142/109323.

Council of Science Editors:

Gentle CM. Internal atomic-scale structure and photothermal dynamics of heterostructured nanomaterials. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2020. Available from: http://hdl.handle.net/2142/109323

29. Wilcox, Daniel E. Chasing Charge Transfer in Organic Systems.

Degree: PhD, Physics, 2015, University of Michigan

URL: http://hdl.handle.net/2027.42/111386

► Charge transfer processes are important in biology, chemistry, and physics. Redox reactions, photosynthesis, the Krebs cycle, and most solar energy harvesting systems depend on intermolecular… (more)

▼ Charge transfer processes are important in biology, chemistry, and physics. Redox reactions, photosynthesis, the Krebs cycle, and most solar energy harvesting systems depend on intermolecular charge transfer. Improved understanding of photoinduced charge transfer may help guide the development of promising technologies such as organic photovoltaics. This dissertation therefore focuses on understanding photoinduced charge transfer and charge separation in organic photovoltaics. Since charge transfer typically takes place on femtosecond to nanosecond timescales, it is difficult to study using electrical methods. However, a wide variety of ultrafast nonlinear optical spectroscopic methods have adequate time resolution. Recently, a generalized pump probe spectroscopy known as time resolved second harmonic generation (TRSHG) has enabled particularly direct measurements of charge transfer. I develop a new version of TRSHG spectroscopy using optical heterodyne detection to reduce sensitivity to stray light and read noise. Using the new TRSHG spectroscopy, I study charge transfer in two different organic photovoltaic systems. In the first study, I examine a boron subphthalocyanine chloride / C60 planar heterojunction, and compare the results to theoretical predictions of charge transfer using a theory based on Fermi’s golden rule (FGR). The comparison sheds light on the microscopic structure of the SubPc / C60 heterojunction. In the second study, I investigate how charge separation changes in a tetraphenyldibenzoperiflanthene / C70 bulk heterojunction as a function of concentration ratio between the two molecules. I show that larger concentrations of C70 help charges separate farther on a sub-nanosecond timescale, before the steady state mobility dominates. All nonlinear spectroscopic methods rely on short pulses of light to achieve the high time resolution necessary to observe ultrafast charge transfer. An ultrafast pulse measurement method is necessary to characterize and optimize the time resolution of nonlinear spectroscopies. I present two new methods for measuring ultrafast pulses: a phase cycled variant of frequency resolved optical gating (FROG) and a method named spectral phase of electric field by analytic reconstruction (SPEAR). I also perform an extensive comparison of pulse measurement methods using a pulse shaper, and identify a few top performers. Advisors/Committee Members: Ogilvie, Jennifer P. (committee member), Shtein, Max (committee member), Geva, Eitan (committee member), Newman, Mark E. (committee member), Forrest, Stephen R. (committee member).

Subjects/Keywords: organic photovoltaics; charge transfer; charge separation; ultrafast spectroscopy; ultrafast pulse measurement; Physics; Science

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APA (6^th Edition):

Wilcox, D. E. (2015). Chasing Charge Transfer in Organic Systems. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/111386

Chicago Manual of Style (16^th Edition):

Wilcox, Daniel E. “Chasing Charge Transfer in Organic Systems.” 2015. Doctoral Dissertation, University of Michigan. Accessed April 12, 2021. http://hdl.handle.net/2027.42/111386.

MLA Handbook (7^th Edition):

Wilcox, Daniel E. “Chasing Charge Transfer in Organic Systems.” 2015. Web. 12 Apr 2021.

Vancouver:

Wilcox DE. Chasing Charge Transfer in Organic Systems. [Internet] [Doctoral dissertation]. University of Michigan; 2015. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/2027.42/111386.

Council of Science Editors:

Wilcox DE. Chasing Charge Transfer in Organic Systems. [Doctoral Dissertation]. University of Michigan; 2015. Available from: http://hdl.handle.net/2027.42/111386

University of Maryland

30. You, Yong Sing. PHYSICAL MECHANISM OF TERAHERTZ GENERATION IN TWO-COLOR PHOTOIONIZATION.

Degree: Chemical Physics, 2014, University of Maryland

URL: http://hdl.handle.net/1903/15194

► Two-color photoionization has been widely used as a versatile tool for intense, broadband terahertz (THz) radiation generation. In this scheme, an ultrashort laser's fundamental and… (more)

▼ Two-color photoionization has been widely used as a versatile tool for intense, broadband terahertz (THz) radiation generation. In this scheme, an ultrashort laser's fundamental and its second harmonic pulses are co-focused into a gas of atoms or molecules, transforming them into plasma by photoionization. This process produces an intense THz pulse emitted in the forward direction. The main focus of this dissertation is to provide a physical understanding of such THz generation and investigate its generation mechanism at both microscopic and macroscopic levels. First, we examine the generation process by measuring the relative phase between two-color (fundamental and second harmonic) laser fields and the resulting THz field simultaneously. We discover that a relative phase of π/2 yields maximal THz outputs, consistent with a semi-classical plasma current model. We find that this optimal relative phase is independent of laser intensities, gas species, and two-color laser amplitude ratios. We also measure concurrent near-field photocurrents. All these measurements verify laser-produced plasma currents as a microscopic source for THz generation. We also investigate THz radiation from an ensemble of aligned air molecules in two-color laser fields. Our experiments show that THz radiation is strongly affected by molecular (nitrogen and oxygen) alignment. We explain this phenomenon in the context of the plasma current model combined with alignment-dependent ionization. Phase-matching is essential to achieve high-efficiency nonlinear frequency conversion. We discover THz generation by two-color photoionization in elongated air plasmas (filamentation) is naturally phase-matched in the off-axis direction, resulting in donut-shaped radiation profiles in the far field. Because of this off-axis phase-matching, THz yields increase almost linearly with the filament length, scalable for further THz energy enhancement. Lastly, we study the polarization of emitted THz radiation. In the case of in-line focusing geometry, we observe the polarization evolves from linear to elliptical with increasing plasma length. This ellipticity arises from two combined effects – successive polarization rotation of local THz plasma sources, caused by laser phase and polarization modulations, and the velocity mismatch between laser and THz, which produces an elliptical THz pulse from a series of time-delayed, polarization-rotating local THz fields. Advisors/Committee Members: Kim, Ki-Yong (advisor).

Subjects/Keywords: Physics; Plasma physics; Optics; optics; Photoionization; Plasmas; terahertz; Ultrafast phenomena; Ultrafast spectroscopy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

You, Y. S. (2014). PHYSICAL MECHANISM OF TERAHERTZ GENERATION IN TWO-COLOR PHOTOIONIZATION. (Thesis). University of Maryland. Retrieved from http://hdl.handle.net/1903/15194

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

You, Yong Sing. “PHYSICAL MECHANISM OF TERAHERTZ GENERATION IN TWO-COLOR PHOTOIONIZATION.” 2014. Thesis, University of Maryland. Accessed April 12, 2021. http://hdl.handle.net/1903/15194.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

You, Yong Sing. “PHYSICAL MECHANISM OF TERAHERTZ GENERATION IN TWO-COLOR PHOTOIONIZATION.” 2014. Web. 12 Apr 2021.

Vancouver:

You YS. PHYSICAL MECHANISM OF TERAHERTZ GENERATION IN TWO-COLOR PHOTOIONIZATION. [Internet] [Thesis]. University of Maryland; 2014. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/1903/15194.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

You YS. PHYSICAL MECHANISM OF TERAHERTZ GENERATION IN TWO-COLOR PHOTOIONIZATION. [Thesis]. University of Maryland; 2014. Available from: http://hdl.handle.net/1903/15194

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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Open Access Theses and Dissertations