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University of Colorado
1.
Jovanovic, Milena.
Conformational Dependence of σ-Electron Delocalization in the Catenae Xnme2n+2, X = Si, Ge, Sn, and Pb.
Degree: PhD, 2019, University of Colorado
URL: https://scholar.colorado.edu/chemistry_gradetds/3 
► Bonds of σ type are the most common chemical bonds, dominating bonding in all molecules and defining the framework of a molecule. It has been…
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▼ Bonds of σ type are the most common chemical bonds, dominating bonding in all molecules and defining the framework of a molecule. It has been long known that electrons in σ bonds can delocalize throughout a molecule. However, the nature of σ-electron delocalization is not fully understood due to its complexity. One of the important aspects of σ-electron delocalization is its conformational dependence, first noted in oligosilanes where properties of a molecule change drastically when it changes conformation. This dissertation describes efforts to understand the conformational dependence of σ delocalization in oligosilanes and their heavier analogs using simple intuitive models and density functional theory (DFT) calculations. The first part of the dissertation focuses on studying the conformational dependence of electron delocalization in oligosilanes. It is shown that oligosilanes can exist as two distinct chromophores, σ-delocalized conformers with large dihedral angles and σ-localized conformers with small dihedral angles. Properties of a conformer are dictated by the shape of frontier molecular orbitals, which is different for conformers with small and large dihedral angles. The origin of the conformational dependence is found in the interplay between two delocalization mechanisms, which can lead to enhancement of delocalization or to its complete annihilation. The second part of the dissertation describes characteristics of σ-electron delocalization in linear infinite polysilane, polygermane, polystannane, and polyplumbane. The conformational dependence of electron delocalization is confirmed in all these molecules. Effective hole mass is used to indicate an extent of the delocalization, while a position of the Fermi level in reciprocal space is used to determine the dominant mechanism of delocalization. The simple model used to explain the origin of the conformational dependence of electron delocalization in saturated compounds is verified by comparison with density functional theory calculations. Relatively simple analysis presented here provides an important insight into properties of a complex ubiquitous phenomenon of delocalization of electrons through σ bonds.
Advisors/Committee Members: Josef Michl, Joel D. Eaves, David Jonas.
Subjects/Keywords: conformational dependence; density functional theory; electron delocalization; helices; ladder c model; σ-electron delocalization; Chemistry; Physical Chemistry; Physics
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APA (6th Edition):
Jovanovic, M. (2019). Conformational Dependence of σ-Electron Delocalization in the Catenae Xnme2n+2, X = Si, Ge, Sn, and Pb. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chemistry_gradetds/3
Chicago Manual of Style (16th Edition):
Jovanovic, Milena. “Conformational Dependence of σ-Electron Delocalization in the Catenae Xnme2n+2, X = Si, Ge, Sn, and Pb.” 2019. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/chemistry_gradetds/3.
MLA Handbook (7th Edition):
Jovanovic, Milena. “Conformational Dependence of σ-Electron Delocalization in the Catenae Xnme2n+2, X = Si, Ge, Sn, and Pb.” 2019. Web. 02 Mar 2021.
Vancouver:
Jovanovic M. Conformational Dependence of σ-Electron Delocalization in the Catenae Xnme2n+2, X = Si, Ge, Sn, and Pb. [Internet] [Doctoral dissertation]. University of Colorado; 2019. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/chemistry_gradetds/3.
Council of Science Editors:
Jovanovic M. Conformational Dependence of σ-Electron Delocalization in the Catenae Xnme2n+2, X = Si, Ge, Sn, and Pb. [Doctoral Dissertation]. University of Colorado; 2019. Available from: https://scholar.colorado.edu/chemistry_gradetds/3
University of Colorado
2.
Midgett, Aaron G.
Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots.
Degree: PhD, Chemistry & Biochemistry, 2011, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/32
► Providing affordable, clean energy is one of the major challenges facing society today, and one of the promising solutions is third generation solar energy…
(more)
▼ Providing affordable, clean energy is one of the major challenges facing society today, and one of the promising solutions is third generation solar energy conversion. Present day, first and second-generation solar cells can at most convert each absorbed photon into a single electron hole pair, thereby establishing a theoretical limit to the power conversion efficiency. The process of multiple exciton generation (MEG) in semiconductor quantum dots increases that theoretical efficiency from 33% to 42% by utilizing the excess energy of high energy photons that is otherwise wasted as heat to excite a second electron-hole pair, thereby boosting the potential photocurrent. This thesis explores the benefits of MEG in quantum confined systems and shows that quantum dots are more efficient at generating multiple excitons from a single photon than bulk semiconductors. The variations in optical measurements of MEG have raised skepticism and brought into question the validity of these experiments. The two important questions that this thesis attempts to address are (1) what are the enhanced QYs in isolated PbSe QDs and (2) does quantum confinement enhance MEG over bulk semiconductors. Experimental variations in the enhanced QYs are partially explained by the production of a long-lived photocharged state that increases the apparent photon-to-exciton QYs. A procedure is detailed that decreases the possibility of producing this charged state. By studying the production of these states, conditions are found that minimize their effect and produce less variation in the reported QYs. Variations in the MEG efficiency were studied in films of chemically treated PbSe quantum dots where a different mechanism was responsible for an apparent decrease of the measured QYs. Finally, for the first time, a quantum dot size-dependence in the MEG efficiency was found in colloidal PbSe, PbS, and PbSxSe1-x quantum dot solutions and is attributed to the increased Coulomb interaction in materials with a larger Bohr exciton radius. These results will allow a better understanding of MEG and how this important process may be used to enhance solar energy conversion.
Advisors/Committee Members: Arthur J. Nozik, David Jonas, Niels H. Damrauer.
Subjects/Keywords: Carrier Multiplication; Multiple Exciton Generation; Nanocrystal; Quantum Dot; Solar Cell; Nanoscience and Nanotechnology; Physical Chemistry
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APA (6th Edition):
Midgett, A. G. (2011). Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/32
Chicago Manual of Style (16th Edition):
Midgett, Aaron G. “Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots.” 2011. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/chem_gradetds/32.
MLA Handbook (7th Edition):
Midgett, Aaron G. “Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots.” 2011. Web. 02 Mar 2021.
Vancouver:
Midgett AG. Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/chem_gradetds/32.
Council of Science Editors:
Midgett AG. Ultrafast Optical Studies of Multiple Exciton Generation in Lead Chalcogenide Quantum Dots. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/chem_gradetds/32
University of Colorado
3.
MacLeod, Matthew Kellar.
Singlet Exciton Delocalization and Localization in Oligosilanes.
Degree: PhD, Chemistry & Biochemistry, 2011, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/42
► The aim of this thesis is to reproduce and interpret the trends in electronic absorption and emission spectra of permethylated oligosilanes by theoretical means.…
(more)
▼ The aim of this thesis is to reproduce and interpret the trends in electronic absorption and emission spectra of permethylated oligosilanes by theoretical means. Longstanding questions concerning the structures responsible for various emissions from electronically excited singlet states that have been observed are addressed. New deactivation mechanisms that allow oligosilanes to return to ground state equilibrium geometries are also presented. The question of how saturated systems accommodate sigma-sigma* excitation is addressed computationally. Finally, new bonding patterns in excited states of oligosilanes have been identied. These include large geometry distortions from the ground state equilibrium structures, rehybridization, and in some cases the involvement of 4s, 4p and 3d Si atomic orbitals results in pentavalent Si for special cases where electronic excitation becomes highly localized.
Advisors/Committee Members: Josef Michl, David Jonas, Robert Parson.
Subjects/Keywords: delocalization; electronic absorption; excited states; exciton; localization; Chemistry
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APA (6th Edition):
MacLeod, M. K. (2011). Singlet Exciton Delocalization and Localization in Oligosilanes. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/42
Chicago Manual of Style (16th Edition):
MacLeod, Matthew Kellar. “Singlet Exciton Delocalization and Localization in Oligosilanes.” 2011. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/chem_gradetds/42.
MLA Handbook (7th Edition):
MacLeod, Matthew Kellar. “Singlet Exciton Delocalization and Localization in Oligosilanes.” 2011. Web. 02 Mar 2021.
Vancouver:
MacLeod MK. Singlet Exciton Delocalization and Localization in Oligosilanes. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/chem_gradetds/42.
Council of Science Editors:
MacLeod MK. Singlet Exciton Delocalization and Localization in Oligosilanes. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/chem_gradetds/42
University of Colorado
4.
Hewitt, Joshua Thomas.
Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes.
Degree: PhD, Chemistry & Biochemistry, 2013, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/77
► A novel ruthenium(II) polypyridyl complex [Ru(bpy-An)(tpy-φ-MV)]4+ (where tpy-An = 4’-(9-anthrcenyl)-2,2’:6’,2’’-terpyridine and tpy-&phi-MV,2+ = 4’-(1-(1’-methyl-4,4-bipyridinium-1-yl)-phenyl)-2,2’:6’,2’’-terpyridine) capable of undergoing energy transfer (EnT) or electron transfer (ET)…
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▼ A novel ruthenium(II) polypyridyl complex [Ru(bpy-An)(tpy-φ-MV)]4+ (where tpy-An = 4’-(9-anthrcenyl)-2,2’:6’,2’’-terpyridine and tpy-&phi-MV,2+ = 4’-(1-(1’-methyl-4,4-bipyridinium-1-yl)-phenyl)-2,2’:6’,2’’-terpyridine) capable of undergoing energy transfer (EnT) or electron transfer (ET) following photoexcitation to the metal-to-ligand charge transfer (MLCT) state is investigated. Adaptive feedback control (AFC) pulse shaping, which has proven to be a versatile experimental tool for probing photoinduced dynamics in a variety of chemical systems, is used try and control the EnT and ET reactivity in this complex with the goal of informing the underlying EnT and ET dynamics. To allow for interpretation of the aforementioned AFC experiments the photophysics of [Ru(bpy-An)(tpy-φ-MV)]4+ and a family of six closely related bis-terpyridine Ru(II) complexes are characterized using static absorption, electochemical, and ultrafast pump-probe techniques. These experiments reveal previously unreported dynamics such as equilibration between the 3MLCT and 3MC (where MC = metal centered excited state) and interligand electron transfer. Furthermore, the EnT and ET reactions in [Ru(bpy-An)(tpy-φ-MV)]4+ (and the associated model complexes) are found to occur on a sub-picosecond and picosecond timescale, respectively. These are the fastest EnT and ET timescales reported for any Ru(II) bis-terpyridine based complexes. As an addendum, photophysics of the mononuclear water oxidation catalysts [Ru(bpy)(tpy)(OH
2)]2+ and [Ru(bpy)(tpy)(OD
2)]2+ in neat H
2O and D
2O solvent, respectively, are reported. Ultrafast pump-probe experiments reveal an inverse kinetic isotope effect with the excited state lifetime being shorter for the D
2O complex than the H
2O complex. This is attributed to interactions between the coordinated aqua (or D
2O) and solvent in the MLCT excited state and suggests design principles applicable to synthesis of photo-driven water oxidation assemblies.
Advisors/Committee Members: Niels H. Damrauer, Garry Rumbles, Gordana Dukovic, David Jonas, Charles Musgrave.
Subjects/Keywords: Physical Chemistry
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APA (6th Edition):
Hewitt, J. T. (2013). Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/77
Chicago Manual of Style (16th Edition):
Hewitt, Joshua Thomas. “Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes.” 2013. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/chem_gradetds/77.
MLA Handbook (7th Edition):
Hewitt, Joshua Thomas. “Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes.” 2013. Web. 02 Mar 2021.
Vancouver:
Hewitt JT. Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/chem_gradetds/77.
Council of Science Editors:
Hewitt JT. Towards the use of Adaptive Feedback Control Pulse Shaping to Probe and Control Reactivity of the Metal-to-Ligand Charge Transfer Excited State in Ruthenium(II) Bis-Terpyridine Complexes. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/chem_gradetds/77
University of Colorado
5.
Benko, Craig Anthony.
Extreme Ultraviolet Frequency Combs for Precision Measurement and Strong-Field Physics.
Degree: PhD, Physics, 2016, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/170
► The extreme ultraviolet (XUV) is a relatively unexplored spectral region for high-resolution laser spectroscopy. Many atomic and molecular systems of fundamental interest lie in…
(more)
▼ The extreme ultraviolet (XUV) is a relatively unexplored spectral region for high-resolution laser spectroscopy. Many atomic and molecular systems of fundamental interest lie in wait of investigation, but the lack of highly coherent sources has forgone the ability to experiment. The XUV frequency comb offers exciting new frontiers for fundamental physics and measurement science by enabling direct and highly coherent laser access to the XUV. Prior to 2012, our group demonstrated the best levels of phase coherence in the XUV at the 10 MHz level and the most powerful XUV light source originating from high-order harmonic generation with powers of 220
μW/harmonic. The work in this thesis improves upon both of these metrics demonstrating coherence at the 62.5 mHz level (eight orders of magnitude improvement) and power levels approaching 1 mW/harmonic (five times improvement). Our work shows that it is possible to produce XUV light with coherence properties that rival that of visible light using the high-order harmonic generation process.
Leveraging XUV frequency comb technology, we also extend the work to probe strong field physics in atomic and molecular systems. We use the phase stable light produced during high-order harmonic generation to probe attosecond phenomena in atoms manifested in the intensity dependent dipole phase. We also study strong-field light-matter interactions in molecular systems. Using our femtosecond enhancement cavities, we perform field-free molecular alignment at unprecedented repetition rates. This allows for a sensitive study of the strong-field interaction and allows the high-order harmonic generation process to be performed in an aligned molecular target.
As XUV frequency comb technology continues to mature, further gains in power levels are anticipated. Additional applications in high-resolution spectroscopy, strong-field physics, solid-state physics, and laser science will come to fruition.
Advisors/Committee Members: Jun Ye, John L. Hall, Andreas Becker, Markus Raschke, David Jonas.
Subjects/Keywords: Atomic; Molecular and Optical Physics
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APA (6th Edition):
Benko, C. A. (2016). Extreme Ultraviolet Frequency Combs for Precision Measurement and Strong-Field Physics. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/170
Chicago Manual of Style (16th Edition):
Benko, Craig Anthony. “Extreme Ultraviolet Frequency Combs for Precision Measurement and Strong-Field Physics.” 2016. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/phys_gradetds/170.
MLA Handbook (7th Edition):
Benko, Craig Anthony. “Extreme Ultraviolet Frequency Combs for Precision Measurement and Strong-Field Physics.” 2016. Web. 02 Mar 2021.
Vancouver:
Benko CA. Extreme Ultraviolet Frequency Combs for Precision Measurement and Strong-Field Physics. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/phys_gradetds/170.
Council of Science Editors:
Benko CA. Extreme Ultraviolet Frequency Combs for Precision Measurement and Strong-Field Physics. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/phys_gradetds/170
University of Colorado
6.
Miller, Michelle R.
Time Resolving Electron Dynamics in Atomic and Molecular Systems Using High-Harmonic Spectroscopy.
Degree: PhD, Physics, 2016, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/190
► The generation of intense, femtosecond-duration laser pulses using near-IR to IR wavelengths of light opened a new frontier of highly nonlinear physics characterized by…
(more)
▼ The generation of intense, femtosecond-duration laser pulses using near-IR to IR wavelengths of light opened a new frontier of highly nonlinear physics characterized by the resolution of electronic dynamics on their natural time scale through the application of attosecond-duration coherent light. These developments were made possible through the strong-field induced phenomenon of high-order harmonic generation (HHG), which results from the tunnel ionization, propagation, and recombination of an electron wavepacket with an atomic or molecular system. By emitting a broad spectrum of coherent radiation, this process enabled the development of attosecond-duration light. Due to its fundamental dependence upon electronic dynamics ongoing within the generative system, high-order harmonic generation has promise as a spectroscopic tool capable of resolving structural and dynamical processes within molecules. In this thesis, we apply numerical methods to study the time-resolution afforded by HHG in atomic and molecular systems. We also develop and validate new methods for simulating the single-electron response of multi-electron systems in the presence of intense laser fields. To begin, we demonstrate the capacity for high-order harmonic generation to function as a signal of the dynamics of a propagating electron wavepacket. Through the use of an isolated attosecond pulse we gate the moment of ionization, selecting for or against electron trajectories that revisit the parent ion multiple times. With this control, we identify spectral and temporal signals which conclusively demonstrate the presence of these multiple revisitations. In addition to imaging electron dynamics during propagation, we also show that high-order harmonic generation can be used to resolve electron dynamics inside of molecules. As driving field sources become available with increasingly long wavelength, electron dynamics in large and conjugated systems show evidence of a highly nonadiabatic response. Using the model system of H
2+, we demonstrate that the frequency-dependent amplitude and phase of emitted high-order harmonic generation is highly demonstrative of these dynamics. The intrinsic frequency chirp of the emitted radiation enables the translation of these spectral alterations into a time-resolved picture of the counterintuitive transient localization of the electron on alternating sides of the molecular system.
Advisors/Committee Members: Andreas Becker, Agnieszka Jaron-Becker, Margaret Murnane, John Bohn, David Jonas.
Subjects/Keywords: high-order harmonic generation; laser pulses; single-electron response; transient localization; Atomic, Molecular and Optical Physics
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APA (6th Edition):
Miller, M. R. (2016). Time Resolving Electron Dynamics in Atomic and Molecular Systems Using High-Harmonic Spectroscopy. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/190
Chicago Manual of Style (16th Edition):
Miller, Michelle R. “Time Resolving Electron Dynamics in Atomic and Molecular Systems Using High-Harmonic Spectroscopy.” 2016. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/phys_gradetds/190.
MLA Handbook (7th Edition):
Miller, Michelle R. “Time Resolving Electron Dynamics in Atomic and Molecular Systems Using High-Harmonic Spectroscopy.” 2016. Web. 02 Mar 2021.
Vancouver:
Miller MR. Time Resolving Electron Dynamics in Atomic and Molecular Systems Using High-Harmonic Spectroscopy. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/phys_gradetds/190.
Council of Science Editors:
Miller MR. Time Resolving Electron Dynamics in Atomic and Molecular Systems Using High-Harmonic Spectroscopy. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/phys_gradetds/190
University of Colorado
7.
Spott, Andrew.
Perturbative and Ab-Initio Calculations of Electrical Susceptibilities of Atoms.
Degree: PhD, Physics, 2017, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/221
► Perturbative nonlinear optics consists of many powerful predictive theoretical methods, in- cluding the perturbative series of observables related to the interaction of light with…
(more)
▼ Perturbative nonlinear optics consists of many powerful predictive theoretical methods, in- cluding the perturbative series of observables related to the interaction of light with matter. The light intensity limits of such series have been studied in the past for highly nonlinear processes such as above threshold ionization and high harmonic generation. A more recent debate focuses on the limits of applicability of perturbation theory for the nonlinear electrical susceptibility and the nonlinear index of refraction of atoms, which are important parameters to study, for example, for filamentation of laser pulses in nonlinear media. In this thesis we analyze theoretical predictions for the electrical susceptibility of atoms for the transition from the perturbative to the nonperturbative intensity regime. To this end, we apply a numerical basis state method that allows us to perform respective calculations in the framework of perturbation theory as well as using ab-initio methods. The results let us identify the intensity at which the application of perturbation theory breaks down. Furthermore, we provide an analysis of the nonlinear susceptibility as a function of time during the interaction with the laser pulse and find that theoretical predictions are in good agreement with recent experimental data.
Advisors/Committee Members: Andreas Becker, Agnieszka Jaron-Becker, David Jonas, Margaret Murnane, Jose D’incao.
Subjects/Keywords: Atomic, Molecular and Optical Physics; Quantum Physics
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APA (6th Edition):
Spott, A. (2017). Perturbative and Ab-Initio Calculations of Electrical Susceptibilities of Atoms. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/221
Chicago Manual of Style (16th Edition):
Spott, Andrew. “Perturbative and Ab-Initio Calculations of Electrical Susceptibilities of Atoms.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/phys_gradetds/221.
MLA Handbook (7th Edition):
Spott, Andrew. “Perturbative and Ab-Initio Calculations of Electrical Susceptibilities of Atoms.” 2017. Web. 02 Mar 2021.
Vancouver:
Spott A. Perturbative and Ab-Initio Calculations of Electrical Susceptibilities of Atoms. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/phys_gradetds/221.
Council of Science Editors:
Spott A. Perturbative and Ab-Initio Calculations of Electrical Susceptibilities of Atoms. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/phys_gradetds/221
University of Colorado
8.
Su, Jing.
Theoretical Analysis and Numerical Simulation of Attosecond Time Delays in Photoionization.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/111
► Recent developments in laser technology, in particular the advances in high-harmonic generation, enable the generation of ultrashort extreme ultraviolet (XUV) pulses with attosecond (1…
(more)
▼ Recent developments in laser technology, in particular the advances in high-harmonic generation, enable the generation of ultrashort extreme ultraviolet (XUV) pulses with attosecond (1 as = 10
−18 s) duration. Such tools open the opportunity to study electron dynamics in atoms and molecules on its intrinsic time scale. As an example, the attosecond streaking technique was recently applied to time resolve the photoionization process in atomic and solid systems. In this technique, an isolated attosecond XUV pulse, that ionizes the electron in the target system, is superimposed with a few-cycle streaking pulse (usually of near-infrared wavelengths). The streaking pulse modulates the final momentum (or energy) of the photoelectron. The measured streaking trace, i.e., the final momentum (or energy) as a function of the relative delay between these two pulses, contains time information of the photoionization process. By comparing two streaking traces measured for photoionization from the 2s and 2p orbitals in a neon atom, Schultze et al. [Science 328, 1658 (2010)] found a temporal offset of 21 ± 5 as between them and interpreted this value as the time delay between photoionization from the 2s and 2p orbitals. This experiment has initiated a debate among theoreticians, in particular about the origin of the measured time delay. A correct interpretation of the delay is extremely important for our understanding of the attosecond streaking technique and an exact analysis of time resolved measurements of this and other ultrafast processes.
In this thesis we systematically study the attosecond time delays in photoionization using numerical simulations. We first propose a new method, based on the fundamental definition of a time delay, to theoretically study the photoionization process induced by an XUV pulse from a time-dependent perspective. We then turn to analyze the time delays measured in streaking experiments. Our results show that for single-photon ionization the observed streaking time delay arises from the finite-range propagation of the photoelectron in the coupled field of the ionic potential and the streaking pulse. Consequently, we conclude that the photon absorption occurs instantaneously at the center of the XUV pulse, i.e., with no time delay. Our analysis further reveals that the streaking time delay can be interpreted as a finite sum of piecewise field-free time delays weighted by the relative instantaneous streaking field strength and provides itself as a useful tool for imaging the presence of an additional potential located at a distance from the ionic core. We finally extend our time delay studies to the two-photon ionization process and show that the absorption time delay is significantly different for nonresonant and resonant two-photon ionization. Our results imply that the absorption of two photons in the nonresonant case occurs instantaneously, without time delay, at the center of the XUV pulse. However, in the resonant scenario we find a substantial absorption time…
Advisors/Committee Members: Andreas Becker, Agnieszka Jaron-Becker, Henry Kapteyn, Steven Cundiff, David Jonas.
Subjects/Keywords: streaking; propagation; absorption; Schrödinger; Wigner-Smith; Atomic, Molecular and Optical Physics
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APA ·
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APA (6th Edition):
Su, J. (2014). Theoretical Analysis and Numerical Simulation of Attosecond Time Delays in Photoionization. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/111
Chicago Manual of Style (16th Edition):
Su, Jing. “Theoretical Analysis and Numerical Simulation of Attosecond Time Delays in Photoionization.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/phys_gradetds/111.
MLA Handbook (7th Edition):
Su, Jing. “Theoretical Analysis and Numerical Simulation of Attosecond Time Delays in Photoionization.” 2014. Web. 02 Mar 2021.
Vancouver:
Su J. Theoretical Analysis and Numerical Simulation of Attosecond Time Delays in Photoionization. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/phys_gradetds/111.
Council of Science Editors:
Su J. Theoretical Analysis and Numerical Simulation of Attosecond Time Delays in Photoionization. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/111
University of Colorado
9.
Buckley, Danielle M.
Carrier Dynamics of Colloidal Solutions and Arrays of Lead Chalcogenide Quantum Dots.
Degree: PhD, Chemistry & Biochemistry, 2014, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/121
► While quantum dots (QDs) potentially offer routes to increase the efficiency of solar energy harvesting, fundamental photophysical processes, such as carrier cooling, are still…
(more)
▼ While quantum dots (QDs) potentially offer routes to increase the efficiency of solar energy harvesting, fundamental photophysical processes, such as carrier cooling, are still not fully understood. Ultrafast degenerate pump-probe spectroscopy is used to investigate carrier dynamics in both isolated colloidal quantum dots, uncoupled quantum dot arrays, and most importantly, coupled quantum dot arrays that may be suitable for device applications. Pumping and probing at the same wavelength overcomes frequency-dependent absorption cross-section issues that may complicate results. Additionally, utilizing novel sample refreshing techniques minimizes photodegradation and photocharging.
The time-dependent behavior of PbS nanocrystal arrays and colloidal solutions is measured at the band gap with sub-100fs time resolution and at higher photon energies with sub-40fs resolution. Different ligand treatments are employed to exchange bulky long-chain organics for shorter chains with different functional groups. Ligand exchange is performed on films as well as a colloidal solution.
Investigations of 2nm diameter PbS quantum dots at the band gap and at 1.4 times the band gap show the biexciton lifetime in an uncoupled array is the same as in colloidal solution. This is in contrast to previous reports of different decay times for various sizes of PbSe QD solutions and uncoupled arrays. Degenerate studies of these same 2nm diameter PbS QDs as coupled arrays at the band gap indicate substantial excited state absorption that increases with increasing pump fluence.
Advisors/Committee Members: David Jonas, Gordana Dukovic, Veronica Vaida, Robert Parson, Henry Kapteyn.
Subjects/Keywords: degenerate pump probe; lead sulfide; quantum dots; ultrafast spectroscopy; Physical Chemistry
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APA (6th Edition):
Buckley, D. M. (2014). Carrier Dynamics of Colloidal Solutions and Arrays of Lead Chalcogenide Quantum Dots. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/121
Chicago Manual of Style (16th Edition):
Buckley, Danielle M. “Carrier Dynamics of Colloidal Solutions and Arrays of Lead Chalcogenide Quantum Dots.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/chem_gradetds/121.
MLA Handbook (7th Edition):
Buckley, Danielle M. “Carrier Dynamics of Colloidal Solutions and Arrays of Lead Chalcogenide Quantum Dots.” 2014. Web. 02 Mar 2021.
Vancouver:
Buckley DM. Carrier Dynamics of Colloidal Solutions and Arrays of Lead Chalcogenide Quantum Dots. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/chem_gradetds/121.
Council of Science Editors:
Buckley DM. Carrier Dynamics of Colloidal Solutions and Arrays of Lead Chalcogenide Quantum Dots. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/chem_gradetds/121
University of Colorado
10.
Ding, Chengyuan.
Bright Coherent Ultrafast Tabletop Light Sources Development and the Application on EUV to Soft X-Ray Absorption Spectroscopy.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/120
► The generation of the advanced bright coherent ultrafast light source from ultraviolet (UV) to soft X-ray have been pursued for decades. It requires the…
(more)
▼ The generation of the advanced bright coherent ultrafast light source from ultraviolet (UV) to soft X-ray have been pursued for decades. It requires the development of light conversion technique, such as high-order harmonics generation (HHG), as well as the driving laser. In this thesis, we first demonstrate the highest pulse energy (10 mJ), single-stage, ultrafast (45 fs) Ti:sapphire amplifier to date, with a repetition rate of 1 kHz. We then use this laser to pump an optical parametric amplifier system and generate 1.3 μm, 30 fs pulses with sufficient energy (2 mJ) for optimally-efficient, phase matched HHG conversion. This allows us to demonstrate the highest flux, soft X-ray HHG source to date with > 106 photons/pulse/1% bandwidth at 1 kHz (corresponding to > 109 photons/s/1% bandwidth) in a broadband, continuum, spectrum extending to 200 eV, through the fully phase matched hollow waveguide geometry HHG. This photon flux represents an approximately 3 orders-of-magnitude increase compared with past work. Meanwhile, due to the experimental similarity, the high energy ultrashort (10 fs) UV source is implemented in parallel to the soft X-ray source by the four wave mixing (FWM) process. The pulse energy (32 uJ) of UV source is increased by more than 3 times compared with past work, with the pulse duration compressible to less than 13 fs. Finally, utilizing the unique bright supercontinuum HHG soft X-ray source, we have demonstrated soft X-ray absorption spectroscopy of multiple elements and transitions in molecules simultaneously, with the ability to resolve near edge fine structure with high fidelity. The Xeon photon-ionization process is also resolved in the EUV transient absorption spectroscopy experiment by tuning the soft X-ray source to the EUV region, which shows the stability, tunability, and applicability of our tabletop extreme nonlinear light source for the time-resolved experiments.
Advisors/Committee Members: Margaret Murnane, Henry Kapteyn, Agnieszka Jaron-Becker, Ralph Jimenez, David Jonas.
Subjects/Keywords: High harmonic generation; Near-edge X-ray absorption fine structure (NEXAFS); Ti:sapphire amplifier; Transient absorption; Ultrafast Soft X-ray generation; Ultrafast UV generation; Physics
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APA (6th Edition):
Ding, C. (2014). Bright Coherent Ultrafast Tabletop Light Sources Development and the Application on EUV to Soft X-Ray Absorption Spectroscopy. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/120
Chicago Manual of Style (16th Edition):
Ding, Chengyuan. “Bright Coherent Ultrafast Tabletop Light Sources Development and the Application on EUV to Soft X-Ray Absorption Spectroscopy.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/phys_gradetds/120.
MLA Handbook (7th Edition):
Ding, Chengyuan. “Bright Coherent Ultrafast Tabletop Light Sources Development and the Application on EUV to Soft X-Ray Absorption Spectroscopy.” 2014. Web. 02 Mar 2021.
Vancouver:
Ding C. Bright Coherent Ultrafast Tabletop Light Sources Development and the Application on EUV to Soft X-Ray Absorption Spectroscopy. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/phys_gradetds/120.
Council of Science Editors:
Ding C. Bright Coherent Ultrafast Tabletop Light Sources Development and the Application on EUV to Soft X-Ray Absorption Spectroscopy. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/120
University of Colorado
11.
Gerrity, Michael R.
Development of a High Energy, kHz, Mid-Infrared OPCPA Laser for keV High Harmonic Generation.
Degree: PhD, Physics, 2015, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/131
► Coherent keV photon energy x-rays have many applications for materials science at the shortest length and time scales. Unfortunately, there are relatively few options…
(more)
▼ Coherent keV photon energy x-rays have many applications for materials science at the shortest length and time scales. Unfortunately, there are relatively few options for coherent x-ray generation. One of the most promising methods is high harmonic generation, wherein a femtosecond driving laser pulse is coherently upconverted to the x-ray region of the spectrum. Recent work has shown that the maximum x-ray photon energy that can be generated via high harmonic generation scales favorably with the wavelength of the driving laser pulse. This has sparked an interest in using mid-infrared (3-5_m) lasers to drive high harmonic generation.
However, high harmonic generation necessitates a mJ level, kHz repetition rate, femtosecond driving laser. At present, there are no such lasers in the mid-infrared region of the spectrum. This necessitates the development of new laser architectures for tabletop coherent x-ray generation.
OPCPA technology is one of the most promising avenues for high energy, high repletion rate lasers in the mid-infrared. This thesis reports on the design and development of a mJ level, kHz repetition rate, femtosecond OPCPA laser running at 3μm, optimized for tabletop coherent x-ray generation.
The system described here integrates and extends a variety of laser technologies towards this goal. The full laser is based upon an Yb:_ber oscillator and MgO:PPLN OPO front end. To pump our OPCPA system, we developed a four stage, cryogenic Yb:YAG laser running with >35mJ of output energy at 1kHz. We then use this to a pump a three stage OPCPA system, likewise running at 1kHz. We demonstrate over 3.4mJ of output energy at 1.55_m, along with 1.4mJ at 3μm. We then show compression of the 3μm output to <110fs. Finally, we conclude with the future directions for this laser, and discuss how it may be scaled to higher energies, shorter pulse lengths, and even further into the mid-infrared.
Advisors/Committee Members: Margaret Murnane, Henry Kapteyn, Sterling Backus, Thomas Schibli, David Jonas.
Subjects/Keywords: mid-IR lasers; OPCPA; Ultrafast lasers; cryogenic laser; Optics; Physics
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APA (6th Edition):
Gerrity, M. R. (2015). Development of a High Energy, kHz, Mid-Infrared OPCPA Laser for keV High Harmonic Generation. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/131
Chicago Manual of Style (16th Edition):
Gerrity, Michael R. “Development of a High Energy, kHz, Mid-Infrared OPCPA Laser for keV High Harmonic Generation.” 2015. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/phys_gradetds/131.
MLA Handbook (7th Edition):
Gerrity, Michael R. “Development of a High Energy, kHz, Mid-Infrared OPCPA Laser for keV High Harmonic Generation.” 2015. Web. 02 Mar 2021.
Vancouver:
Gerrity MR. Development of a High Energy, kHz, Mid-Infrared OPCPA Laser for keV High Harmonic Generation. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/phys_gradetds/131.
Council of Science Editors:
Gerrity MR. Development of a High Energy, kHz, Mid-Infrared OPCPA Laser for keV High Harmonic Generation. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/phys_gradetds/131
University of Colorado
12.
Konold, Patrick Eugene.
Ultrafast Nonlinear Spectroscopy of Red Fluorescent Proteins.
Degree: PhD, Chemistry & Biochemistry, 2015, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/147
► Red-emitting homologues (RFPs) of the native Green Fluorescent Protein (GFP) with emission wavelengths beyond 650 nm are desirable probes for in vivo imaging experiments.…
(more)
▼ Red-emitting homologues (RFPs) of the native Green Fluorescent Protein (GFP) with emission wavelengths beyond 650 nm are desirable probes for
in vivo imaging experiments. They offer the potential for deeper tissue penetration and lower background scatter given a cleaner spectral window. However, bioimaging applications are hindered by poor photophysics (
e.g. low fluorescence quantum yield, high photobleaching), which limits experimental resolution and represents a significant obstacle towards utilization for low copy-number, long-duration imaging applications. In this thesis, a variety of femtosecond nonlinear electronic spectroscopies were employed jointly with site-directed mutagenesis to investigate the photophysical properties of RFPs. In one study, the molecular mechanism of red emission was pursued in two notable RFPs, mPlum and TagRFP675. Solvation dynamics observed with time-resolved transient grating spectroscopy were interpreted with the aid of molecular dynamics simulations to indicate that their red-emission is correlated with the ability of specific chromophore-sidechain hydrogen-bonding interactions to interconvert between direct and water-mediated states. In a second set of studies, two-dimensional double quantum coherence spectroscopy was used to probe the electronic transitions of mPlum. It was discovered that it displayed a response distinctly different from an organic dye in bulk solvent. Modeling indicate of these spectra indicate the spectral features may be attributed to the existence of multiple high-lying (n>1) excited states. The results provide new insight into the electronic structure of these widely used fluorescent probes.
Advisors/Committee Members: Ralph Jimenez, Steven Cundiff, David Jonas, Niels Damrauer, Robert Parson.
Subjects/Keywords: Multidimensional spectroscopy; Solvation dynamics; Stokes shift; Biophysics; Physical Chemistry; Physics
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APA (6th Edition):
Konold, P. E. (2015). Ultrafast Nonlinear Spectroscopy of Red Fluorescent Proteins. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/147
Chicago Manual of Style (16th Edition):
Konold, Patrick Eugene. “Ultrafast Nonlinear Spectroscopy of Red Fluorescent Proteins.” 2015. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/chem_gradetds/147.
MLA Handbook (7th Edition):
Konold, Patrick Eugene. “Ultrafast Nonlinear Spectroscopy of Red Fluorescent Proteins.” 2015. Web. 02 Mar 2021.
Vancouver:
Konold PE. Ultrafast Nonlinear Spectroscopy of Red Fluorescent Proteins. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/chem_gradetds/147.
Council of Science Editors:
Konold PE. Ultrafast Nonlinear Spectroscopy of Red Fluorescent Proteins. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/chem_gradetds/147
University of Colorado
13.
Wilker, Molly Bea.
Charge Transfer Dynamics in Complexes of Light-Absorbing CdS Nanorods and Redox Catalysts.
Degree: PhD, Chemistry & Biochemistry, 2015, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/154
► The use of photoexcited electrons and holes in semiconductor nanocrystals as reduction and oxidation reagents is an intriguing way of harvesting photon energy to…
(more)
▼ The use of photoexcited electrons and holes in semiconductor nanocrystals as reduction and oxidation reagents is an intriguing way of harvesting photon energy to drive chemical reactions. This dissertation describes research efforts to understand the photoexcited charge transfer kinetics in complexes of colloidal CdS nanorods coupled with either a water oxidation or reduction catalyst. The first project focuses on the charge transfer interactions between photoexcited CdS nanorods and a mononuclear water oxidation catalyst derived from the [Ru(bpy)(tpy)Cl]
+ parent structure. Upon excitation, hole transfer from CdS oxidizes the catalyst (Ru
2+→Ru
3+) on a 100 ps – 1 ns timescale. This is followed by a 10 – 100 ns electron transfer that reduces the Ru
3+ center. The relatively slow electron transfer dynamics may provide opportunities for accumulation of the multiple holes at the catalyst, which is necessary for water oxidation. The second project details the electron transfer kinetics in complexes of CdS nanorods coupled with [FeFe]-hydrogenase, which catalyzes H
+ reduction
. These complexes photochemically produce H
2 with quantum yields of up to 20%. The kinetics of electron transfer from CdS nanorods to hydrogenase play a critical role in the overall photochemical reactivity, as the quantum efficiency of electron transfer defines the upper limit on the quantum yield of H
2 generation. For optimized complexes, the electron transfer rate constant and the electron relaxation rate constant in CdS nanorods are comparable, with values of ≈107 s
−1, resulting in a quantum efficiency of electron transfer of 42%. Insights from these time-resolved spectroscopic studies are used to discuss the intricate kinetic pathways involved in photochemical H
2 generation in photocatalytic complexes. Finally, experimental results from photodriven H
2 generation and measurements of nanocrystal excited state lifetimes when the length of the nanocrystal-surface ligand was varied provide a deeper understanding into the mechanism for electron transfer from photoexcited nanorods to hydrogenase.
Advisors/Committee Members: Gordana Dukovic, Niels Damrauer, David Jonas, Joel Eaves, Paul King.
Subjects/Keywords: Biomimetic; Photoluminescence; Transient Absorption; Chemistry; Nanoscience and Nanotechnology; Physical Chemistry
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APA (6th Edition):
Wilker, M. B. (2015). Charge Transfer Dynamics in Complexes of Light-Absorbing CdS Nanorods and Redox Catalysts. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/154
Chicago Manual of Style (16th Edition):
Wilker, Molly Bea. “Charge Transfer Dynamics in Complexes of Light-Absorbing CdS Nanorods and Redox Catalysts.” 2015. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/chem_gradetds/154.
MLA Handbook (7th Edition):
Wilker, Molly Bea. “Charge Transfer Dynamics in Complexes of Light-Absorbing CdS Nanorods and Redox Catalysts.” 2015. Web. 02 Mar 2021.
Vancouver:
Wilker MB. Charge Transfer Dynamics in Complexes of Light-Absorbing CdS Nanorods and Redox Catalysts. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/chem_gradetds/154.
Council of Science Editors:
Wilker MB. Charge Transfer Dynamics in Complexes of Light-Absorbing CdS Nanorods and Redox Catalysts. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/chem_gradetds/154
University of Colorado
14.
Schnitzenbaumer, Kyle J.
The Impact of Chalcogenide Ligands on the Photoexcited States of Cadmium Chalcogenide Quantum Dots.
Degree: PhD, Chemistry & Biochemistry, 2015, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/159
► Quantum dots (QDs) are the foundation of many optoelectronic devices because their optical and electronic properties are synthetically tunable. The inherent connection between synthetically…
(more)
▼ Quantum dots (QDs) are the foundation of many optoelectronic devices because their optical and electronic properties are synthetically tunable. The inherent connection between synthetically controllable physical parameters, such as size, shape, and surface chemistry, and QD electronic properties provides flexibility in manipulating excited states. The properties of the ligands that passivate the QD surface and provide such synthetic control, however, are quite different from those that are beneficial for use in optoelectronic devices. In these applications, ligands that promote charge transfer are desired. To this end, significant research efforts have focused on post-synthetic ligand exchange to shorter, more conductive ligand species. Surface ligand identity, however, is a physical parameter intimately tied to QD excited state behavior in addition to charge transfer. A particularly interesting group of ligands, due to the extraordinarily thin ligand shell they create around the QD, are the chalcogenides S
2-, Se
2-, and Te
2-. While promising, little is known about how these chalcogenide ligands affect QD photoexcited states. This dissertation focuses on the impact of chalcogenide ligands on the excited state dynamics of cadmium chalcogenide QDs and associated implications for charge transfer. This is accomplished through a combination of theoretical (Chapters 2, 3, and 6) and experimental (Chapters 2, 4, 5 and 6) methods. We establish a theoretical foundation for describing chalcogenide capped QD photoexcited states and measure the dynamics of these excited states using transient absorption spectroscopy. The presented results highlight the drastic effects surface modification can have on QD photoexcited state dynamics and provide insights for more informed design of optoelectronic systems.
Advisors/Committee Members: Gordana Dukovic, David Jonas, Veronica Bierbaum, Robert Parson, Henry Kapteyn.
Subjects/Keywords: Chalcogenide Ligands; Photophysics; Quantum Dots; Transient Absorption Spectroscopy; Physical Chemistry
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APA (6th Edition):
Schnitzenbaumer, K. J. (2015). The Impact of Chalcogenide Ligands on the Photoexcited States of Cadmium Chalcogenide Quantum Dots. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/159
Chicago Manual of Style (16th Edition):
Schnitzenbaumer, Kyle J. “The Impact of Chalcogenide Ligands on the Photoexcited States of Cadmium Chalcogenide Quantum Dots.” 2015. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/chem_gradetds/159.
MLA Handbook (7th Edition):
Schnitzenbaumer, Kyle J. “The Impact of Chalcogenide Ligands on the Photoexcited States of Cadmium Chalcogenide Quantum Dots.” 2015. Web. 02 Mar 2021.
Vancouver:
Schnitzenbaumer KJ. The Impact of Chalcogenide Ligands on the Photoexcited States of Cadmium Chalcogenide Quantum Dots. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/chem_gradetds/159.
Council of Science Editors:
Schnitzenbaumer KJ. The Impact of Chalcogenide Ligands on the Photoexcited States of Cadmium Chalcogenide Quantum Dots. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/chem_gradetds/159
University of Colorado
15.
Lin, Yiheng.
Quantum Entanglement Generation in Trapped Ions Using Coherent and Dissipative Methods.
Degree: PhD, Physics, 2015, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/150
► Entangled states are a key resource in fundamental quantum physics, quantum cryptography, and quantum computation. In this thesis, we focus on the demonstrations of…
(more)
▼ Entangled states are a key resource in fundamental quantum physics, quantum cryptography, and quantum computation. In this thesis, we focus on the demonstrations of two novel methods to generate entanglement. First, we implement dissipative production of a maximally entangled steady state on two trapped ions. Dissipative and coherent processes are combined and implemented in a continuous time-independent fashion, analogous to optical pumping of atomic states, continuously driving the system towards the steady entangled state. With this method, we obtain a Bell state fidelity up to 0.89(2). Second, we propose and demonstrate a novel coherent process to confine quantum evolution in a subspace between an initial separable state and the target entangled state. We demonstrate this scheme on two and three ions obtaining a Bell state fidelity up to 0.992(2). Both of these methods are robust against certain types of experimental noise and decoherence. Additionally, we demonstrate sympathetic cooling of ion chains to near the ground
state of motion with an electromagnetically-induced-transparency (EIT) method. This results in roughly an order of magnitude faster cooling time while using significantly lower laser power compared to the conventional resolved sideband cooling method. These techniques may be helpful for scaled-up quantum computing.
Advisors/Committee Members: David J. Wineland, James Thompson, Cindy Regal, Eric Cornell, David Jonas.
Subjects/Keywords: open quantum system; quantum computing; quantum entanglement; quantum information; quantum optics; trapped ion experiment; Atomic, Molecular and Optical Physics; Optics; Quantum Physics
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APA ·
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APA (6th Edition):
Lin, Y. (2015). Quantum Entanglement Generation in Trapped Ions Using Coherent and Dissipative Methods. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/150
Chicago Manual of Style (16th Edition):
Lin, Yiheng. “Quantum Entanglement Generation in Trapped Ions Using Coherent and Dissipative Methods.” 2015. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/phys_gradetds/150.
MLA Handbook (7th Edition):
Lin, Yiheng. “Quantum Entanglement Generation in Trapped Ions Using Coherent and Dissipative Methods.” 2015. Web. 02 Mar 2021.
Vancouver:
Lin Y. Quantum Entanglement Generation in Trapped Ions Using Coherent and Dissipative Methods. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/phys_gradetds/150.
Council of Science Editors:
Lin Y. Quantum Entanglement Generation in Trapped Ions Using Coherent and Dissipative Methods. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/phys_gradetds/150
University of Colorado
16.
Xia, Yuqing.
Multielectron Effects in Strong Field Processes in Molecules.
Degree: PhD, Physics, 2016, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/163
► Laser technology has experienced a rapid evolution in available intensities, frequencies, and pulse durations over the last three decades. Many new laser induced phenomena…
(more)
▼ Laser technology has experienced a rapid evolution in available intensities, frequencies, and pulse durations over the last three decades. Many new laser induced phenomena in atoms have been discovered, such as multiphoton ionization, above-threshold ionization, high-order harmonic generation etc. For the interaction with atoms, usually only one electron in the outermost shell is assumed to be active (called single-active-electron approximation) while all other electrons are considered to remain frozen in their initial states. Due to the extra degrees of freedom (vibration and rotation) and the more complex structures, the interaction of molecules with intense laser pulses reveals many new features. Recent experiments have indicated that electrons from inner valence orbitals of molecules can have significant contributions to ionization and high harmonic generation. Theoretical analysis of these processes in molecules faces the challenge to extend previous theories developed for the atomic case by including the multielectron character of the molecular target.
In this thesis we systematically investigate multielectron effects in the interaction of molecules with intense laser light. To this end, we apply time-dependent density-functional theory to solve the multielectron Schrödinger equation and analyze highly nonlinear processes such as high harmonic generation, laser-induced ionization and nonadiabatic electron localization. Based on the results of our numerical simulations we predict a new feature in the harmonic spectra of molecules, namely the occurrence of fractional harmonics in the form of Mollow sidebands. Such additional peaks in the spectra appear due to a field-induced resonant coupling of an inner valence orbital with the outermost orbital in a molecule. Furthermore, we show that the theoretical explanation of recent experimental data for the ellipticity of high harmonics in N
2 and CO
2 require the systematic consideration of all inner valence shells as well as the proper alignment distribution in the experiment. We also show that the coupling of molecular orbitals in the field can lead to an enhancement of (inner-shell) ionization, potentially leading to a population inversion in the ion, as well as nonadiabatic electron dynamics, where the electron can be trapped at one side of the molecule over several field cycles. Finally, we present the development of a new intense-field theory based on the Floquet theorem with complex Gaussian basis sets and show results of first applications for ionization of simple systems.
Advisors/Committee Members: Agnieszka Jaron-Becker, Andreas Becker, David Jonas, Henry Kapteyn, Jose P. D'Incao.
Subjects/Keywords: laser technology; electron behavior; shell activity; multielectron effects; Mollow sidebands; Atomic, Molecular and Optical Physics
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APA ·
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MLA ·
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CSE |
Export
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Manager
APA (6th Edition):
Xia, Y. (2016). Multielectron Effects in Strong Field Processes in Molecules. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/163
Chicago Manual of Style (16th Edition):
Xia, Yuqing. “Multielectron Effects in Strong Field Processes in Molecules.” 2016. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/phys_gradetds/163.
MLA Handbook (7th Edition):
Xia, Yuqing. “Multielectron Effects in Strong Field Processes in Molecules.” 2016. Web. 02 Mar 2021.
Vancouver:
Xia Y. Multielectron Effects in Strong Field Processes in Molecules. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/phys_gradetds/163.
Council of Science Editors:
Xia Y. Multielectron Effects in Strong Field Processes in Molecules. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/phys_gradetds/163
University of Colorado
17.
Ni, Hongcheng.
Theoretical Studies of Ultrafast Correlated Electron Dynamics in Single and Double Photoionization.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/112
► Recent advances in laser technology have led to the generation of attosecond laser pulses, whose duration is in the range of the natural time…
(more)
▼ Recent advances in laser technology have led to the generation of attosecond laser pulses, whose duration is in the range of the natural time scale of electron dynamics, and thus make the observation and even control of electron dynamics in atoms and molecules possible. While the single-electron dynamics is more thoroughly studied, the correlated dynamics of two electrons is less understood, especially in the context of resolving the ultrafast temporal information in double photoionization. In this thesis, we first study the energy exchange via electron correlation upon photon absorption over large distances in the two-site double photoionization of the helium dimer, which is found to be a two-step process. In the first step, one electron in one atom absorbs the photon and gets ionized. In the second step, this electron propagates towards the neighboring atom and knocks out the other electron. We then introduce the Hamiltonian reduction method to further study the effects of different interactions in the single and double photoionization of the helium dimer. Next, we analyze the selection rules for the emission of two electrons from the helium atom, the helium dimer, and general molecules following the absorption of a few photons in an intense laser field. In particular, the back-to-back emission of the two electrons with equal energy sharing is either suppressed or not depending on the number of photons absorbed from the field.
Finally, we study the time delay between the single and double photoionization processes. We first propose a self-consistent-time method to account for the Coulomb-laser coupling effect and obtain the intrinsic photoabsorption time delay measured by the attosecond streak camera. We then proceed to time resolve the correlated emission of two electrons in the knockout process of the helium dimer with respect to the first step of single ionization.
Advisors/Committee Members: Andreas Becker, Margaret Murnane, Steven T. Cundiff, John L. Bohn, David Jonas.
Subjects/Keywords: attosecond laser; Hamiltonian reduction method; helium dimer; 4D model; coupling effect; selection rules; Atomic, Molecular and Optical Physics
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APA (6th Edition):
Ni, H. (2014). Theoretical Studies of Ultrafast Correlated Electron Dynamics in Single and Double Photoionization. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/112
Chicago Manual of Style (16th Edition):
Ni, Hongcheng. “Theoretical Studies of Ultrafast Correlated Electron Dynamics in Single and Double Photoionization.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/phys_gradetds/112.
MLA Handbook (7th Edition):
Ni, Hongcheng. “Theoretical Studies of Ultrafast Correlated Electron Dynamics in Single and Double Photoionization.” 2014. Web. 02 Mar 2021.
Vancouver:
Ni H. Theoretical Studies of Ultrafast Correlated Electron Dynamics in Single and Double Photoionization. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/phys_gradetds/112.
Council of Science Editors:
Ni H. Theoretical Studies of Ultrafast Correlated Electron Dynamics in Single and Double Photoionization. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/112
University of Colorado
18.
Hogle, William Craig.
High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/118
► To fully understand atomic and molecular dynamics scientists must be able to probe and study dynamics on their fundamental time scales. The motion, structure,…
(more)
▼ To fully understand atomic and molecular dynamics scientists must be able to probe and study dynamics on their fundamental time scales. The motion, structure, and arrangement of molecules play a fundamental role in chemical reactions. Analyzing these reactions is not only important for their immediate insights but the understanding is essential for the progress of many areas of science and technology including biology, material science, and medicine.
These dynamics require a light source with not only the time resolution to capture attosecond and femtosecond dynamics but one that can also reach a large energy range of interesting processes. High harmonic generation (HHG) provides a tunable coherent light source of high energy photons while remaining table-top in size. These highly excited states can be fully analyzed using coincidence electron and ion spectroscopy performed short time-scale resolution.
The combination of high harmonic generation with coincidence spectroscopy allows for the study of a variety of atomic and molecular systems. We were able to observe a new ionization pathway enabled by intense laser fields in argon and xenon. With helium, we demonstrate the ability to optically induce full electromagnetic transparency. The time resolved dissociation of bromine allowed for the understanding of how molecular orbital structure changes to become atomic in nature. In hydrogen we considered the interaction of electronic and nuclear wavepackets in a non-Born-Oppenheimer regime in a new level of detail. We explore the coherent control in dissociating a triatomic molecule with N
2O showing the ability to optically control the dissociation pathway of the molecule. Additional molecules including the argon dimer, ethylene and ozone have also been studied and analysis points to very interesting dynamics.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Andreas Becker, Agnieszka Jaron-Becker, David Jonas.
Subjects/Keywords: atomic dynamics; molecular dynamics; molecular arrangement; high harmonic generation; electromagnetic transparency; dissociation pathway; Atomic, Molecular and Optical Physics
Record Details
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Record Details
Similar Records
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Hogle, W. C. (2014). High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/118
Chicago Manual of Style (16th Edition):
Hogle, William Craig. “High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 02, 2021.
https://scholar.colorado.edu/phys_gradetds/118.
MLA Handbook (7th Edition):
Hogle, William Craig. “High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics.” 2014. Web. 02 Mar 2021.
Vancouver:
Hogle WC. High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 02].
Available from: https://scholar.colorado.edu/phys_gradetds/118.
Council of Science Editors:
Hogle WC. High Harmonic Driven Attosecond and Femtosecond Molecular Dynamics. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/118
. 
Open Access Theses and Dissertations