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University of Colorado
1.
Willett, Kyle William.
OH Masers from Andromeda to the Peak of Cosmic Star Formation.
Degree: PhD, Astrophysical & Planetary Sciences, 2011, University of Colorado
URL: https://scholar.colorado.edu/astr_gradetds/6 
► OH masers are naturally-occurring phenomena powered by stimulated emission, existing in a variety of astrophysical environments. The presence of powerful OH megamasers (OHMs) is…
(more)
▼ OH masers are naturally-occurring phenomena powered by stimulated emission, existing in a variety of astrophysical environments. The presence of powerful OH megamasers (OHMs) is associated with merging galaxies and extreme star formation, while the high luminosities and narrow beams of masers make them powerful probes of local physical conditions. I present research on three projects concentrating on observations of extragalactic OH masers.
The first project analyzes mid-infrared spectroscopy of OHM host galaxies with data from the Spitzer Space Telescope. I identify several mid-infrared spectral features that signal the presence of an OHM, including deep silicate absorption and steep continuum emission, indicating the presence of large amounts of warm dust. Mid-infrared data are also used to test new OH pumping models, demonstrating that OHM hosts favor a smooth, highly embedded dust geometry. Secondly, I describe results of a radio-wavelength survey using the Green Bank Telescope for new OHMs at redshift z ∼ 1. Detections of two new OHMs are included, while statistics of galaxies in which OH was not detected constrain the OHM fraction and overall galaxy merger rate. Finally, I present data from the first OH survey of M31 (the Andromeda galaxy) using the Very Large Array. We found no OH masers above a 5σ = 10 mJy limit in the galaxy. I discuss our results in the context of ongoing efforts to use masers as tools for measuring M31’s proper motion with respect to the Milky Way.
Advisors/Committee Members: Jeremy Darling, John Bally, Heather Lewandowski.
Subjects/Keywords: hydroxyl; masers; megamasers; merging galaxies; OHM; Astrophysics and Astronomy; External Galaxies
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APA (6th Edition):
Willett, K. W. (2011). OH Masers from Andromeda to the Peak of Cosmic Star Formation. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/astr_gradetds/6
Chicago Manual of Style (16th Edition):
Willett, Kyle William. “OH Masers from Andromeda to the Peak of Cosmic Star Formation.” 2011. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/astr_gradetds/6.
MLA Handbook (7th Edition):
Willett, Kyle William. “OH Masers from Andromeda to the Peak of Cosmic Star Formation.” 2011. Web. 28 Nov 2020.
Vancouver:
Willett KW. OH Masers from Andromeda to the Peak of Cosmic Star Formation. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/astr_gradetds/6.
Council of Science Editors:
Willett KW. OH Masers from Andromeda to the Peak of Cosmic Star Formation. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/astr_gradetds/6
University of Colorado
2.
Sinclair, Laura Cathleen.
Development of Frequency Comb Velocity-Modulation Spectroscopy, Spectroscopy of HfF+ and the JILA eEDM Experiment.
Degree: PhD, Physics, 2011, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/48
► Broad bandwidth, precision spectroscopy of the molecular ions of interest to the JILA electron electric dipole moment experiment, HfF+ and ThF+, is necessary due…
(more)
▼ Broad bandwidth, precision spectroscopy of the molecular ions of interest to the JILA electron electric dipole moment experiment, HfF
+ and ThF
+, is necessary due to the limited amount of spectroscopic information available and the large theoretical uncertainties in the energy level structure (thousands of wavenumbers). This thesis covers the development of a novel spectroscopic technique, frequency comb velocity-modulation spectroscopy, that provides high resolution, broad spectral bandwidth, ion discrimination and high sensitivity simultaneously. Frequency comb velocity-modulation spectroscopy as well as single frequency velocity-modulation spectroscopy have been used to identify five rotational bands of HfF
+. This work discusses the first spectroscopic information for HfF
+ which came from our measurement of the
1Π
1 –
1Σ
+ (0,0) band recorded with single-frequency velocity modulation spectroscopy with a sensitivity of 3x10
-7 Hz
-1/2. The development of frequency comb velocity-modulation spectroscopy allowed us to cover a thousand wavenumbers of spectral bandwidth and to identify an additional four HfF
+ bands. The achieved sensitivity for frequency-comb velocity-modulation spectroscopy was 4x10
-8 Hz
-1/2 (spectral element)
-1/2 with 1500 simultaneous detection channels spanning 150 cm
-1 of bandwidth. For a 30 minute acquisition time using 30 interleaved images to densely sample the whole spectrum, this corresponded to a 3x10
-7 single-pass fractional absorption sensitivity for each of the 45,000 measurement channels. The spectroscopic information from all five HfF
+ rotational bands is presented and molecular constants for the
1Σ
+,
3Π
1, and
1Π
1 states were extracted.
Advisors/Committee Members: Eric A. Cornell, Jun Ye, Heather Lewandowski.
Subjects/Keywords: Hafnium fluoride; molecular ions; spectroscopy; Atomic, Molecular and Optical Physics
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APA (6th Edition):
Sinclair, L. C. (2011). Development of Frequency Comb Velocity-Modulation Spectroscopy, Spectroscopy of HfF+ and the JILA eEDM Experiment. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/48
Chicago Manual of Style (16th Edition):
Sinclair, Laura Cathleen. “Development of Frequency Comb Velocity-Modulation Spectroscopy, Spectroscopy of HfF+ and the JILA eEDM Experiment.” 2011. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/phys_gradetds/48.
MLA Handbook (7th Edition):
Sinclair, Laura Cathleen. “Development of Frequency Comb Velocity-Modulation Spectroscopy, Spectroscopy of HfF+ and the JILA eEDM Experiment.” 2011. Web. 28 Nov 2020.
Vancouver:
Sinclair LC. Development of Frequency Comb Velocity-Modulation Spectroscopy, Spectroscopy of HfF+ and the JILA eEDM Experiment. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/phys_gradetds/48.
Council of Science Editors:
Sinclair LC. Development of Frequency Comb Velocity-Modulation Spectroscopy, Spectroscopy of HfF+ and the JILA eEDM Experiment. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/phys_gradetds/48
University of Colorado
3.
Scheer, Adam Michael.
Thermal Decomposition Mechanisms of Lignin Model Compounds: From Phenol to Vanillin.
Degree: PhD, Physics, 2011, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/55
► Lignin is a complex, aromatic polymer abundant in cellulosic biomass (trees, switchgrass etc.). Thermochemical breakdown of lignin for liquid fuel production results in undesirable…
(more)
▼ Lignin is a complex, aromatic polymer abundant in cellulosic biomass (trees, switchgrass etc.). Thermochemical breakdown of lignin for liquid fuel production results in undesirable polycyclic aromatic hydrocarbons that lead to tar and soot byproducts. The fundamental chemistry governing these processes is not well understood. We have studied the unimolecular thermal decomposition mechanisms of aromatic lignin model compounds using a miniature SiC tubular reactor. Products are detected and characterized using time-of-flight mass spectrometry with both single photon (118.2 nm; 10.487 eV) and 1 + 1 resonance-enhanced multiphoton ionization (REMPI) as well as matrix isolation infrared spectroscopy. Gas exiting the heated reactor (300 K – 1600 K) is subject to a free expansion after a residence time of approximately 100 µs. The expansion into vacuum rapidly cools the gas mixture and allows the detection of radicals and other highly reactive intermediates. By understanding the unimolecular fragmentation patterns of phenol (C
6H
5OH), anisole (C
6H
5OCH
3) and benzaldehyde (C
6H
5CHO), the more complicated thermocracking processes of the catechols (HO-C
6H
4-OH), methoxyphenols (HO-C
6H
4-OCH
3) and hydroxybenzaldehydes (HO-C
6H
4-CHO) can be interpreted. These studies have resulted in a predictive model that allows the interpretation of vanillin, a complex phenolic ether containing methoxy, hydroxy and aldehyde functional groups. This model will serve as a guide for the pyrolyses of larger systems including lignin monomers such as coniferyl alcohol. The pyrolysis mechanisms of the dimethoxybenzenes (H<sub>3C-C
6H
4-OCH
3) and syringol, a hydroxydimethoxybenzene have also been studied. These results will aid in the understanding of the thermal fragmentation of sinapyl alcohol, the most complex lignin monomer. </sub> In addition to the model compound work, pyrolyisis of biomass has been studied via the pulsed laser ablation of poplar wood. With the REMPI scheme, aromatic lignin decomposition products are directly and selectively detected. A number of these products are the lignin model compounds listed above, providing a direct link between the model compound studies and the pyrolysis of actual biomass.
Advisors/Committee Members: Gayfree Barney Ellison, Mark R. Nimlos, Heather Lewandowski.
Subjects/Keywords: Aromatic growth; Aryl ether; Biomass; Laser ablation; Lignin; Pyrolysis; Chemistry; Physics
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APA (6th Edition):
Scheer, A. M. (2011). Thermal Decomposition Mechanisms of Lignin Model Compounds: From Phenol to Vanillin. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/55
Chicago Manual of Style (16th Edition):
Scheer, Adam Michael. “Thermal Decomposition Mechanisms of Lignin Model Compounds: From Phenol to Vanillin.” 2011. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/phys_gradetds/55.
MLA Handbook (7th Edition):
Scheer, Adam Michael. “Thermal Decomposition Mechanisms of Lignin Model Compounds: From Phenol to Vanillin.” 2011. Web. 28 Nov 2020.
Vancouver:
Scheer AM. Thermal Decomposition Mechanisms of Lignin Model Compounds: From Phenol to Vanillin. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/phys_gradetds/55.
Council of Science Editors:
Scheer AM. Thermal Decomposition Mechanisms of Lignin Model Compounds: From Phenol to Vanillin. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/phys_gradetds/55
University of Colorado
4.
Ashby, Ava.
The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method.
Degree: MS, Physics, 2016, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/165
► The general impedance method developed by Khondker et.al [1] is applied to multiple barrier potentials to study the transmission behaviors of a single Gaussian…
(more)
▼ The general impedance method developed by Khondker et.al [1] is applied to multiple barrier potentials to study the transmission behaviors of a single Gaussian barrier potential, double rectangular barrier potential, and a double Gaussian barrier potential. Using the impedance method we will find quantum mechanical transmission behaviors like resonant tunneling for the quasi bound-states of the double barrier potentials. The single Gaussian barrier potential is an approximation for the atomtronic battery and the double Gaussian barrier potential is an approximation for the atomtronic transistor. Thus far, the atomtronic work presented in reference [2] was done in the classical regime where thermal currents dominate. The work presented in this thesis analyzes the quantum mechanical characteristics, such as tunneling, to be incorporated and perhaps used to explore coherent transistor action.
Advisors/Committee Members: Dana Anderson, Heather Lewandowski, Charles Rogers.
Subjects/Keywords: atomtronics; impedance method; numerical method; quantum mechanical transmission probablity; Physics
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APA (6th Edition):
Ashby, A. (2016). The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/165
Chicago Manual of Style (16th Edition):
Ashby, Ava. “The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method.” 2016. Masters Thesis, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/phys_gradetds/165.
MLA Handbook (7th Edition):
Ashby, Ava. “The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method.” 2016. Web. 28 Nov 2020.
Vancouver:
Ashby A. The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method. [Internet] [Masters thesis]. University of Colorado; 2016. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/phys_gradetds/165.
Council of Science Editors:
Ashby A. The Study of Modeled Atomtronic Barrier Potentials Through the Impedance Method. [Masters Thesis]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/phys_gradetds/165
University of Colorado
5.
Martin, Joshua Paul.
Photofragmentation and Recombination Dynamics of Partially-Solvated Anionic Clusters.
Degree: PhD, Chemistry & Biochemistry, 2012, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/63
► Photofragmentation studies of mass-selected, partially-solvated anionic clusters are performed to investigate solvent-number specific perturbations to the dissociation dynamics of anionic chromophores. Two anion solutes…
(more)
▼ Photofragmentation studies of mass-selected, partially-solvated anionic clusters are performed to investigate solvent-number specific perturbations to the dissociation dynamics of anionic chromophores. Two anion solutes are employed in the studies reported here: IBr
− and the chemically-related ICN
−. While the former has been the subject of earlier photodissociation studies, ICN
− has not been studied previously. Replacing Br with CN allows the possibilities of isomerization to INC
− and rotational excitation of a photofragment. Two quite different solvents, CO
2 and Ar, are utilized in the experiments. The CO
2 solvent is bound to the chromophore by ~200 meV. Its charge distribution gives rise to substantial electric quadrupole and higher moments that can modify the electronic structure of the solute ion. The Ar solvent is much more weakly bound to the solute (~50 meV), has no permanent multipole moments, and no possibility of rotational, vibrational or electronic excitation in the dissociation process. The contrasting photodissociation dynamics associated with the different combinations of these solutes and solvents reported in this Dissertation both provides new understanding and raises questions concerning photoprocesses in partially solvated ionic complexes.
Following 430 to 650 nm excitation of ICN
− to its
2Π
1/2 excited state, the predominant ionic photoproduct is I
−, with a minor CN
− component. Photodissociation of ICN
− (Ar)<em>
n</em> ,
n = 1–5, results in dominant I
− and I
−(Ar)
n ionic photoproducts, the observation of single-solvent cage recombination for
n = 1, and highly solvated I
− and ICN
− photoproducts. The experimental results, electronic structure calculations, and quantum dynamics calculations together indicate that efficient transfer of a significant amount (> 0.3 eV) of the photoexcitation energy into rotation of the CN diatom occurs following dissociation of the chromophore.
Photofragmentation studies of ICN
− (CO
2)<em>
n</em> ,
n = 1–18, following 400, 500, and 600 nm excitation examine the influence of long-range solute-solvent interactions on the dissociation dynamics. While the dominant fragment from ICN
− excitation is I
−, the addition of even one CO
2 solvent results in dominant CN
−-based photoproducts. Significant cage recombination products are observed for
n = 3, 4, and 7 following 600, 500, and 400 nm excitation. Solvent evaporation experiments show that the average CO
2 solvent binding energy to the ICN
− chromophore is ~200 meV, consistent with earlier experiments on diatomic solutes.
Advisors/Committee Members: W. Carl Lineberger, Robert Parson, Veronica Bierbaum, Barney Ellison, Heather Lewandowski.
Subjects/Keywords: IBr-; ICN-; Partially-Solvated Anionic Clusters; Photofragmentation Dynamics; Recombination Dynamics; Time-resolved; Physical Chemistry
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APA (6th Edition):
Martin, J. P. (2012). Photofragmentation and Recombination Dynamics of Partially-Solvated Anionic Clusters. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/63
Chicago Manual of Style (16th Edition):
Martin, Joshua Paul. “Photofragmentation and Recombination Dynamics of Partially-Solvated Anionic Clusters.” 2012. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/chem_gradetds/63.
MLA Handbook (7th Edition):
Martin, Joshua Paul. “Photofragmentation and Recombination Dynamics of Partially-Solvated Anionic Clusters.” 2012. Web. 28 Nov 2020.
Vancouver:
Martin JP. Photofragmentation and Recombination Dynamics of Partially-Solvated Anionic Clusters. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/chem_gradetds/63.
Council of Science Editors:
Martin JP. Photofragmentation and Recombination Dynamics of Partially-Solvated Anionic Clusters. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/chem_gradetds/63
University of Colorado
6.
Cumby, Tyler Dunnington.
Exploring Few-body Scattering Resonances in a Bose-Fermi Mixture: from Feshbach Dimers to Efimov Trimers.
Degree: PhD, Physics, 2012, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/69
► This thesis presents experiments exploring Feshbach molecules and Efimov trimers in an ultracold Bose-Fermi atomic gas mixture of 40K and 87Rb. These bound states…
(more)
▼ This thesis presents experiments exploring Feshbach molecules and Efimov trimers in an ultracold Bose-Fermi atomic gas mixture of 40K and 87Rb. These bound states are accessed via scattering resonances, called Fano-Feshbach resonances, which arise as a consequence of a bound state being tuned through degeneracy with the threshold energy of colliding atoms. In addition to allowing the tunability of interactions, the Fano-Feshbach resonance allows for a weakly bound molecule state, called the Feshbach molecule state, to be populated. The efficiency of conversion to the Feshbach molecule state depends upon the rate with which the bound state energy is swept through degeneracy with atomic threshold energy. In regions of large scattering lengths, three-body bound states, called Efimov states, also influence inelastic Bose-Bose-Fermi collisions and boson+molecule collisions in our system. The work presented in this thesis utilizes a magnetically tunable Fano-Feshbach resonance to study Feshbach molecule creation in the perturbative limit (the limit of fast magnetic-field sweeps) and the saturated limit (the limit of slow sweeps), where a phenomenological model is applied to understand the conversion efficiency as well as the quantum degeneracy of the molecules. In addition, I present a study of boson+molecule collision rates and Bose-Bose-Fermi collision rates in order to observe signatures of Efimov states and compare against results in the gas mixture
41K-
87Rb to address the question of universality of the three-body parameter in heteronuclear gas mixtures.
Advisors/Committee Members: Deborah Jin, Eric Cornell, John Bohn, Heather Lewandowski, W. Carl Lineberger.
Subjects/Keywords: Efimov; Feshbach; Atomic, Molecular and Optical Physics
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APA (6th Edition):
Cumby, T. D. (2012). Exploring Few-body Scattering Resonances in a Bose-Fermi Mixture: from Feshbach Dimers to Efimov Trimers. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/69
Chicago Manual of Style (16th Edition):
Cumby, Tyler Dunnington. “Exploring Few-body Scattering Resonances in a Bose-Fermi Mixture: from Feshbach Dimers to Efimov Trimers.” 2012. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/phys_gradetds/69.
MLA Handbook (7th Edition):
Cumby, Tyler Dunnington. “Exploring Few-body Scattering Resonances in a Bose-Fermi Mixture: from Feshbach Dimers to Efimov Trimers.” 2012. Web. 28 Nov 2020.
Vancouver:
Cumby TD. Exploring Few-body Scattering Resonances in a Bose-Fermi Mixture: from Feshbach Dimers to Efimov Trimers. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/phys_gradetds/69.
Council of Science Editors:
Cumby TD. Exploring Few-body Scattering Resonances in a Bose-Fermi Mixture: from Feshbach Dimers to Efimov Trimers. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/phys_gradetds/69
University of Colorado
7.
Fitch, Noah J.
Traveling-Wave Stark-Decelerated Molecular Beams for Cold Collision Experiments.
Degree: PhD, Physics, 2013, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/96
► Research of cold and ultracold molecules is currently a burgeoning field in experimental and theoretical physics. New experimental techniques, involving an increasingly large set…
(more)
▼ Research of cold and ultracold molecules is currently a burgeoning field in experimental and theoretical physics. New experimental techniques, involving an increasingly large set of molecule types under high levels of control, are currently opening up new avenues of research with a vast array of potential applications. From understanding the role of quantum mechanics in molecular scattering and cold chemistry, to testing the fundamental symmetries of nature and realizing quantum computing with dipolar molecular qubits, experiments are accessing regimes not dreamed of even a few years ago. Theoretical interest and computing capabilities are also at an all time high, spurred on by the possibility of creating ultracold dipolar gases as tunable realizations of strongly interacting quantum Hamiltonians, creating exotic phases of matter, and the investigation of controlling molecular interactions with applied electromagnetic fields.
Less than a decade ago, cold molecule experiments had seemingly reached a technological plateau, being capable of creating moderate densities of 10
6-10
7 molecules/cm
3 at temperatures of 10-100 mK. With many applications requiring colder temperatures and higher densities, the field was ripe for new advances. Today, via a plethora of methods such as direct molecular laser cooling, electro-optical cooling, magneto- and photo-association, and new molecular beam deceleration techniques, the field is just beginning to have the tools capable of producing truly interesting systems for study.
This work will discuss a couple of major steps taken in the direction of achieving scientific goals using cold molecules. The first experimental advancement discussed will be the development of a co-trap environment for studying interactions and collisions between ultracold atoms and Stark decelerated cold polar molecules. In this experiment, rubidium atoms are trapped using magnetic fields, and ammonia atoms are decelerated and trapped using electric fields. The two traps are spatially overlapped in order to investigate inter-species interactions. The co-trap environment provides exceedingly long interaction times, many orders of magnitude longer than typical beam-based interaction studies. As a result, it provides extremely high sensitivity to weak interaction mechanisms. The second experimental advancement discussed will be the development and construction of a new style of Stark decelerator, capable of producing much larger densities of cold molecules. This apparatus has the potential to expand the realm of possible experiments with chemically interesting species, and provide an unprecedented amount of control over molecular beams and traps. The gains haven't come easily though, as a new class of custom high-voltage amplifiers have needed to be developed. This part of the experiment alone took approximately two years of consistent effort to bring to fruition. After many years of development, this experiment is poised to come online, finally fulfilling its…
Advisors/Committee Members: Heather Lewandowski, Eric Cornell, Jun Ye, Debbie Jin, Carl Lineberger.
Subjects/Keywords: Cold Collisions; Molecular Beams; Stark Deceleration; Traveling Wave; Atomic, Molecular and Optical Physics
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APA (6th Edition):
Fitch, N. J. (2013). Traveling-Wave Stark-Decelerated Molecular Beams for Cold Collision Experiments. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/96
Chicago Manual of Style (16th Edition):
Fitch, Noah J. “Traveling-Wave Stark-Decelerated Molecular Beams for Cold Collision Experiments.” 2013. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/phys_gradetds/96.
MLA Handbook (7th Edition):
Fitch, Noah J. “Traveling-Wave Stark-Decelerated Molecular Beams for Cold Collision Experiments.” 2013. Web. 28 Nov 2020.
Vancouver:
Fitch NJ. Traveling-Wave Stark-Decelerated Molecular Beams for Cold Collision Experiments. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/phys_gradetds/96.
Council of Science Editors:
Fitch NJ. Traveling-Wave Stark-Decelerated Molecular Beams for Cold Collision Experiments. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/phys_gradetds/96
University of Colorado
8.
Gopalakrishnan, Maithreyi.
Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni.
Degree: MS, Physics, 2016, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/171
► Even twenty years after the discovery of ultrafast demagnetization of ferromagnetic materials induced by a femtosecond laser pulse there is still an ongoing debate…
(more)
▼ Even twenty years after the discovery of ultrafast demagnetization of ferromagnetic materials induced by a femtosecond laser pulse there is still an ongoing debate about the mechanisms that drive the process. Surprisingly, a comprehensive study that compares demagnetization dynamics in different materials on equal footing is lacking. Yet, the scientific community would greatly benefit from such study. We fill this gap by performing a systematic comparison of ultrafast demagnetization behavior in Iron, Cobalt and Nickel, the simplest itinerant ferromagnets, under a wide range of pump fluences. In this experiment, we utilize a tabletop broadband extreme ultraviolet source to probe magnetization dynamics at the M2,3 absorption edges of these three elements using the transverse magneto-optical Kerr effect. The obtained data can be used to inform theory and, thereby, assist in resolving the remaining questions about the micro- and macroscopic mechanisms behind ultrafast laser-induced magnetization dynamics in materials.
Advisors/Committee Members: Margaret M. Murnane, Henry C. Kapteyn, Heather Lewandowski, Steven J. Pollock.
Subjects/Keywords: Harmonic; Laser; Magnetism; Spin; Temperature; Ultrafast; Condensed Matter Physics; Optics
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APA (6th Edition):
Gopalakrishnan, M. (2016). Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/171
Chicago Manual of Style (16th Edition):
Gopalakrishnan, Maithreyi. “Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni.” 2016. Masters Thesis, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/phys_gradetds/171.
MLA Handbook (7th Edition):
Gopalakrishnan, Maithreyi. “Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni.” 2016. Web. 28 Nov 2020.
Vancouver:
Gopalakrishnan M. Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni. [Internet] [Masters thesis]. University of Colorado; 2016. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/phys_gradetds/171.
Council of Science Editors:
Gopalakrishnan M. Comparative Study of Laser-Induced Ultrafast Demagnetization Dynamics in Fe, Co, and Ni. [Masters Thesis]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/phys_gradetds/171
University of Colorado
9.
Blanshan, Eric M.
Development of a Compact Cold-Atom Atomic Clock Based on Coherent Population Trapping.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/124
► Field-grade atomic clocks capable of primary standard performance in compact physics packages would be of significant value in a variety of applications ranging from…
(more)
▼ Field-grade atomic clocks capable of primary standard performance in compact physics packages would be of significant value in a variety of applications ranging from network synchronization and secure communications to GPS hold-over and inertial navigation. A cold-atom coherent population trapping (CACPT) clock featuring laser-cooled
87RB atoms and pulsed Ramsey interrogation is a strong candidate for this technology if the principal frequency shifts can be controlled and the performance degradation associated with miniaturization can be overcome. In this thesis, research focused on the development of this type of compact atomic clock is presented. To address the low atom numbers obtained in small cold-atom sources, experiments were performed in which an atomic beam was decelerated with bichromatic stimulated laser forces and loaded into a mm-scale magneto-optical trap, increasing the atom number by a factor of 12.5x. A CACPT clock using the high-contrast lin||lin optical interrogation technique was developed and achieved a stability of 7 × 10
-13 after one hour of integration. Doppler shifts in the clock are explained using a simple kinematic model and canceled by interrogating the atoms with a counter-propagating CPT configuration. Finally, a thorough characterization of the AC-stark effect in lin||lin CPT was performed. Observed shifts are explained in terms of contributions from coherent CPT-generating couplings and population transfer effects caused by optical pumping from incoherent light. Measurements are compared with existing and new theoretical treatments, and a laser configuration is identified that reduces clock drift from light shifts to less than 10
-14 for the current system.
Advisors/Committee Members: Andreas Becker, John Kitching, Neil Ashby, Heather Lewandowski, Y.C. Lee.
Subjects/Keywords: Atomic; Molecular and Optical Physics
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APA (6th Edition):
Blanshan, E. M. (2014). Development of a Compact Cold-Atom Atomic Clock Based on Coherent Population Trapping. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/124
Chicago Manual of Style (16th Edition):
Blanshan, Eric M. “Development of a Compact Cold-Atom Atomic Clock Based on Coherent Population Trapping.” 2014. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/phys_gradetds/124.
MLA Handbook (7th Edition):
Blanshan, Eric M. “Development of a Compact Cold-Atom Atomic Clock Based on Coherent Population Trapping.” 2014. Web. 28 Nov 2020.
Vancouver:
Blanshan EM. Development of a Compact Cold-Atom Atomic Clock Based on Coherent Population Trapping. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/phys_gradetds/124.
Council of Science Editors:
Blanshan EM. Development of a Compact Cold-Atom Atomic Clock Based on Coherent Population Trapping. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/124
University of Colorado
10.
Wilcox, Bethany Rae.
New Tools for Investigating Student Learning in Upper-division Electrostatics.
Degree: PhD, Physics, 2015, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/135
► Student learning in upper-division physics courses is a growing area of research in the field of Physics Education. Developing effective new curricular materials and…
(more)
▼ Student learning in upper-division physics courses is a growing area of research in the field of Physics Education. Developing effective new curricular materials and pedagogical techniques to improve student learning in upper-division courses requires knowledge of both what material students struggle with and what curricular approaches help to overcome these struggles. To facilitate the course transformation process for one specific content area – upper-division electrostatics – this thesis presents two new methodological tools: (1) an analytical framework designed to investigate students' struggles with the advanced physics content and mathematically sophisticated tools/techniques required at the junior and senior level, and (2) a new multiple-response conceptual assessment designed to measure student learning and assess the effectiveness of different curricular approaches.
We first describe the development and theoretical grounding of a new analytical framework designed to characterize how students use mathematical tools and techniques during physics problem solving. We apply this framework to investigate student difficulties with three specific mathematical tools used in upper-division electrostatics: multivariable integration in the context of Coulomb's law, the Dirac delta function in the context of expressing volume charge densities, and separation of variables as a technique to solve Laplace's equation. We find a number of common themes in students' difficulties around these mathematical tools including: recognizing when a particular mathematical tool is appropriate for a given physics problem, mapping between the specific physical context and the formal mathematical structures, and reflecting spontaneously on the solution to a physics problem to gain physical insight or ensure consistency with expected results.
We then describe the development of a novel, multiple-response version of an existing conceptual assessment in upper-division electrostatics courses. The goal of this new version is to provide an easily-graded electrostatics assessment that can potentially be implemented to investigate student learning on a large scale. We show that student performance on the new multiple-response version exhibits a significant degree of consistency with performance on the free-response version, and that it continues to provide significant insight into student reasoning and student difficulties. Moreover, we demonstrate that the new assessment is both valid and reliable using data from upper-division physics students at multiple institutions. Overall, the work described in this thesis represents a significant contribution to the methodological tools available to researchers and instructors interested in improving student learning at the upper-division level.
Advisors/Committee Members: Steven J. Pollock, Noah Finkelstein, Heather Lewandowski, Paul Beale, Eric Stade.
Subjects/Keywords: ACER Framework; Assessment development; Mathematics; Multiple-response CUE; Physics Education; Student learning; Higher Education; Physics; Science and Mathematics Education
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APA (6th Edition):
Wilcox, B. R. (2015). New Tools for Investigating Student Learning in Upper-division Electrostatics. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/135
Chicago Manual of Style (16th Edition):
Wilcox, Bethany Rae. “New Tools for Investigating Student Learning in Upper-division Electrostatics.” 2015. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/phys_gradetds/135.
MLA Handbook (7th Edition):
Wilcox, Bethany Rae. “New Tools for Investigating Student Learning in Upper-division Electrostatics.” 2015. Web. 28 Nov 2020.
Vancouver:
Wilcox BR. New Tools for Investigating Student Learning in Upper-division Electrostatics. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/phys_gradetds/135.
Council of Science Editors:
Wilcox BR. New Tools for Investigating Student Learning in Upper-division Electrostatics. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/phys_gradetds/135
University of Colorado
11.
Thompson, Michael.
Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy.
Degree: PhD, 2018, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/260
► The interactions of anionic species with other molecules opens up new avenues to study the process of bond formation or charge transfer. Gas phase…
(more)
▼ The interactions of anionic species with other molecules opens up new avenues to study the process of bond formation or charge transfer. Gas phase clusters are a useful tool for studying such systems in the absence of competing effects in condensed phase. Cluster ions can be studied as model analogues to more complex condensed phase systems. The majority of this thesis focuses on gas phase cluster ions of the form [M(CO
2)
n] (M=Bi, Sn, Mn, Fe). These clusters consist of a charged molecular anion surrounded by weakly bound “solvent” CO
2 species. IR photodissociation spectroscopy is used to probe the infrared spectra of the molecular core ions. [Bi(CO
2)
n]
- and [Sn(CO
2)
n]
- clusters are studied as model systems of the reduction of CO
2 at a corner or edge site of a Bi or Sn electrode surface. The structures of the core ions for these clusters give insight into potential docking motifs of the CO
2 species. In both species, the formation of an ɳ
1-C docked CO
2 species results in a metal carboxylate complex. These structures have characteristic CO
2 stretching frequencies that can be used to identify these species in the condensed phase. These species also exhibit oxalate ligand formation, which is interesting since it requires the formation of a C-C bond. [Mn(CO
2)
n]
- and [Fe(CO
2)
n]
‑ clusters are studied to understand how a change in the electron configuration of the metal affects the binding motifs of the CO
2. As in other first row transition metals, these species exhibit a rich collection of interaction motifs, among which the ɳ
2 (C,O), where M-C and M-O bonds are formed, is most prevalent. In addition, oxalate ligands also are present. We also investigated the structure and charge distributions of neat and heterogeneous N
2O clusters [(N
2O)
n- and (N
2O)
nO
-]. In heterogeneous N
2O clusters, we find that initially the core ion is an NNO
2- molecular anion. We find that this core ion switches to an O- core ion at larger cluster sizes. We also find an N
2O
- core ion for neat anionic clusters of N
2O and report for the first time frequencies of the N-N and N-O stretches of the N
2O
- anion.
Advisors/Committee Members: J. Mathias Weber, Carl Lineberger, Veronica M. Bierbaum, Heather Lewandowski, Niels H. Damrauer.
Subjects/Keywords: species; anion; electron; molecular; infrared photodissociation spectroscopy; Chemistry; Physical Chemistry
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APA (6th Edition):
Thompson, M. (2018). Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/260
Chicago Manual of Style (16th Edition):
Thompson, Michael. “Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy.” 2018. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/chem_gradetds/260.
MLA Handbook (7th Edition):
Thompson, Michael. “Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy.” 2018. Web. 28 Nov 2020.
Vancouver:
Thompson M. Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/chem_gradetds/260.
Council of Science Editors:
Thompson M. Core Ion Structures in CO2- and N2O-Based Cluster Anions Studied by Infrared Photodissociation Spectroscopy. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/chem_gradetds/260
University of Colorado
12.
Kaufman, Sydney Hamilton.
Photodissociation Spectroscopy of Anionic Transition Metal Complexes.
Degree: PhD, Chemistry & Biochemistry, 2013, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/105
► Transition metal complexes play an important role in many aspects of chemistry; whether in supporting biological functions, as catalysts for organic reactions, in the…
(more)
▼ Transition metal complexes play an important role in many aspects of chemistry; whether in supporting biological functions, as catalysts for organic reactions, in the environment, or in industry. This thesis is comprised of gas-phase spectroscopic studies of four transition metal species with implications for many different chemical applications.
Most knowledge of the target molecules in this thesis are derived from studies in the condensed phase, where the chemical environment can change molecular properties. As a result, it is difficult to gain an understanding of the intrinsic properties in solution as well as a molecular-level picture of chemical reactions that take place where many oxidation states, molecular species, and solvent interactions occur. By isolating one particular species in the gas phase, we are able to observe how each species interacts with light independent of perturbing effects of solvent and counter ions.
In this thesis, we perform spectroscopic experiments on mass-selected ions in the gas phase, where we are able to gain information on intrinsic molecular properties without the influence of a condensed phase chemical environment.
We employ photodissociation spectroscopy, where we mass-select a particular ionic species from solution and irradiate that molecular ion with the output of a tunable laser in the ultraviolet and visible regions. By monitoring the fragments produced, we can obtain an electronic absorption spectrum of the isolated species as well as gain insight into the photochemistry of the ions under study from the fragmentation pathways observed. We combine this method with solution absorption spectra as well as electronic structure calculations.
Advisors/Committee Members: J. Mathias Weber, G. Barney Ellison, Neils Damrauer, Carl W. Lineberger, Heather Lewandowski.
Subjects/Keywords: Gas-phase spectroscopy; Transition Metals; Physical Chemistry; Physics
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APA (6th Edition):
Kaufman, S. H. (2013). Photodissociation Spectroscopy of Anionic Transition Metal Complexes. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/105
Chicago Manual of Style (16th Edition):
Kaufman, Sydney Hamilton. “Photodissociation Spectroscopy of Anionic Transition Metal Complexes.” 2013. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/chem_gradetds/105.
MLA Handbook (7th Edition):
Kaufman, Sydney Hamilton. “Photodissociation Spectroscopy of Anionic Transition Metal Complexes.” 2013. Web. 28 Nov 2020.
Vancouver:
Kaufman SH. Photodissociation Spectroscopy of Anionic Transition Metal Complexes. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/chem_gradetds/105.
Council of Science Editors:
Kaufman SH. Photodissociation Spectroscopy of Anionic Transition Metal Complexes. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/chem_gradetds/105
University of Colorado
13.
Adams, Christopher Lynn.
Photoelectron Spectroscopy of Nitroalkane Anions.
Degree: PhD, Physics, 2011, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/181
► This thesis describes research on the electronic properties of nitroalkane anions, CH3(CH2)nNO2 (where n=0,1,2, and 3), using a newly built velocity-map imaging photoelectron spectrometer.…
(more)
▼ This thesis describes research on the electronic properties of nitroalkane anions, CH
3(CH
2)
nNO
2 (where n=0,1,2, and 3), using a newly built velocity-map imaging photoelectron spectrometer. The nitroalkanes are an intriguing class of molecules that possess many similarities owing to the dominating presence of the nitro group. They all possess relatively low adiabatic electron affinities, large dipole moments, and undergo similar distortions (largely localized within the nitro group) upon electron attachment. The focus of the studies presented in this thesis is quantitatively characterizing the anion and neutral states, determining fundamental molecular properties (i.e., adiabatic electron affinities, bond dissociation energies, vertical detachment energies, etc.), and highlighting some of the interesting dynamics that the nitroalkane anions can exhibit using photoelectron spectroscopy.
The first two studies present the photoelectron spectra of nitromethane and nitroethane anions. As these molecules are small enough to be tractable by a more involved theoretical analysis, ab initio theory and Franck-Condon simulations were utilized to simulate and interpret the photoelectron spectra. In order for the simulations to achieve good agreement with the experimental spectra, additional efforts were directed at characterizing the torsional potentials of the methyl and ethyl groups and predicting the contribution of torsional motion to the photoelectron spectra. These investigations led to new assignments for the adiabatic electron affinities, the first observation of their dipole-bound states in photoelectron spectra, and determinations of the C-NO
2 bond dissociation energies for the nitromethane and nitroethane anion.
The third study presents the photoelectron spectra of nitropropane and nitrobutane anions. Each of these molecules possesses a number of stable anion and neutral conformers. Ab initio theory and Franck-Condon simulations were employed to identify possible conformations responsible for the dominant features in the photoelectron spectra. Finally, an anomalous feature belonging to a separate photoelectron emission pathway was identified in the photoelectron spectrum using spectra obtained at different photon energies and through an analysis of the angular distributions.
The nitroalkane anions possess adiabatic electron affinities that are smaller than the transition energies of their fundamental CH stretching modes. As a consequence, excitation of one of these modes will lead to vibrational autodetachment that is facilitated by intramolecular vibrational excitation. The last study presents vibrational autodetachment photoelectron spectra of the nitromethane anion. The spectra were analyzed using several simple models to extract some of the important underlying information regarding the intramolecular vibrational relaxation occurring prior to vibrational autodetachment.
Advisors/Committee Members: J. Mathias Weber, Veronica M. Bierbaum, W. Carl Lineberger, G. Barney Ellison, Heather Lewandowski.
Subjects/Keywords: anion; nitroalkane; nitromethane; velocity map imaging; Atomic, Molecular and Optical Physics; Chemistry; Physical Chemistry
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APA (6th Edition):
Adams, C. L. (2011). Photoelectron Spectroscopy of Nitroalkane Anions. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/181
Chicago Manual of Style (16th Edition):
Adams, Christopher Lynn. “Photoelectron Spectroscopy of Nitroalkane Anions.” 2011. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/phys_gradetds/181.
MLA Handbook (7th Edition):
Adams, Christopher Lynn. “Photoelectron Spectroscopy of Nitroalkane Anions.” 2011. Web. 28 Nov 2020.
Vancouver:
Adams CL. Photoelectron Spectroscopy of Nitroalkane Anions. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/phys_gradetds/181.
Council of Science Editors:
Adams CL. Photoelectron Spectroscopy of Nitroalkane Anions. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/phys_gradetds/181
University of Colorado
14.
Zutz, Amelia Marie.
Quantum State-Resolved Collision Dynamics of Nitric Oxide at Ionic Liquid and Molten Metal Surfaces.
Degree: PhD, 2017, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/218
► Detailed molecular scale interactions at the gas–liquid interface are explored with quantum state-to-state resolved scattering of a jet-cooled beam of NO(2Π1/2; N = 0)…
(more)
▼ Detailed molecular scale interactions at the gas–liquid interface are explored with quantum state-to-state resolved scattering of a jet-cooled beam of NO(
2Π
1/2; N = 0) from ionic liquid and molten metal surfaces. The scattered distributions are probed via laser-induced fluorescence methods, which yield rotational and spin-orbit state populations that elucidate the dynamics of energy transfer at the gas-liquid interface. These collision dynamics are explored as a function of incident collision energy, surface temperature, scattering angle, and liquid identity, all of which are found to substantially affect the degree of rotational, electronic and vibrational excitation of NO via collisions at the liquid surface.
Rotational distributions observed reveal two distinct scattering pathways, (i) molecules that trap, thermalize and eventually desorb from the surface (trapping-desorption, TD), and (ii) those that undergo prompt recoil (impulsive scattering, IS) prior to complete equilibration with the liquid surface. Thermally desorbing NO molecules are found to have rotational temperatures close to, but slightly cooler than the surface temperature, indicative of rotational dependent sticking probabilities on liquid surfaces. Nitric oxide is a radical with multiple low-lying electronic states that serves as an ideal candidate for exploring nonadiabatic state-changing collision dynamics at the gas-liquid interface, which induce significant excitation from ground (
2Π
1/2) to excited (
2Π
3/2) spin–orbit states. Molecular beam scattering of supersonically cooled NO from hot molten metals (Ga and Au, Ts = 300 – 1400 K) is also explored, which provide preliminary evidence for vibrational excitation of NO mediated by thermally populated electron-hole pairs in the hot, conducting liquid metals. The results highlight the presence of electronically nonadiabatic effects and build toward a more complete characterization of energy transfer dynamics at gas-liquid interfaces.
Advisors/Committee Members: David J. Nesbitt, William C. Lineberger, Eric Cornell, Heather Lewandowski, Barney Ellison.
Subjects/Keywords: gas-liquid interface; liquid surface; Physical Chemistry
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APA (6th Edition):
Zutz, A. M. (2017). Quantum State-Resolved Collision Dynamics of Nitric Oxide at Ionic Liquid and Molten Metal Surfaces. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/218
Chicago Manual of Style (16th Edition):
Zutz, Amelia Marie. “Quantum State-Resolved Collision Dynamics of Nitric Oxide at Ionic Liquid and Molten Metal Surfaces.” 2017. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/chem_gradetds/218.
MLA Handbook (7th Edition):
Zutz, Amelia Marie. “Quantum State-Resolved Collision Dynamics of Nitric Oxide at Ionic Liquid and Molten Metal Surfaces.” 2017. Web. 28 Nov 2020.
Vancouver:
Zutz AM. Quantum State-Resolved Collision Dynamics of Nitric Oxide at Ionic Liquid and Molten Metal Surfaces. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/chem_gradetds/218.
Council of Science Editors:
Zutz AM. Quantum State-Resolved Collision Dynamics of Nitric Oxide at Ionic Liquid and Molten Metal Surfaces. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/chem_gradetds/218
University of Colorado
15.
Nelson, Daniel John.
Photoelectron Spectroscopy of Organic Aromatic Anions.
Degree: PhD, Chemistry & Biochemistry, 2017, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/235
► Nelson, Daniel John (Ph.D. Chemical Physics) Photoelectron Spectroscopy of Organic Aromatic Anions Thesis directed by Professor W. Carl Lineberger This dissertation reports and interprets…
(more)
▼ Nelson, Daniel John (Ph.D. Chemical Physics)
Photoelectron Spectroscopy of Organic Aromatic Anions
Thesis directed by Professor W. Carl Lineberger
This dissertation reports and interprets the results of experiments in which photoelectron spectroscopy was performed on a variety of aromatic anions. In addition to these photoelectron studies, the results and conclusions of an experiment in which HCl is scattered off atomically flat Au (111) surfaces are also presented.
Photoelectron spectroscopy of the isomers of methylphenoxide reveals that these molecules display minimal vibrational excitation upon photodetachment, accessing the electronic ground and first excited state of the corresponding radicals. The photoelectron spectra of
p-methylphenoxide reveal a photon energy dependence arising from electron autodetachment. The slow electron velocity map imaging (SEVI) technique was employed to obtain the electron affinities (EAs) of these radicals with an uncertainty of 1.4 meV. Combining the measured EAs with previously measured O–H bond dissociation energies in a thermodynamic cycle allows for the measurement of the acidities of the methylphenols with an uncertainty that is an order of magnitude smaller than any previous measurement.
The full interpretation of the photoelectron spectra of the isomers of methylenephenoxide presents a far greater challenge with many subtleties. The EAs of
o- and
p-methylenephenoxyl were measured and shown to be ~1 eV lower in energy than for the methylphenoxyls, implying that the electron withdrawing effect of the CH
2 group in the methylenephenoxides attracts electron density from the oxygen site via resonance, as compared to the methylphenoxides. The singlet–triplet splittings of the diradicals
o- and
p-methylenephenoxyl were measured. The acidities of the methylenephenols were measured by acid bracketing. Combining the EAs of the methylenephenoxyls with these acidities allows for a measurement of the weak O-H bond dissociation energy of the methylenephenols.
The photoelectron spectra of indolide were obtained and interpreted. The structure of indolide minimally distorts upon electron photodetachment accessing the electronic ground doublet state of indolyl. The EA of indolyl was measured utilizing the SEVI technique with an uncertainty of 1.7 meV. Ring distortion vibrational modes were found to be excited upon electron photodetachment. The previously measured acidity of indole is combined with our measurement of the EA of indolyl to determine the N–H bond dissociation energy of indole.
Advisors/Committee Members: William C. Lineberger, Veronica M. Bierbaum, J. M. Weber, Jun Ye, Heather Lewandowski.
Subjects/Keywords: aromatic radicals; ion chemistry; ion-neutral chemistry; photoelectron spectroscopy; spectroscopy; thermochemistry; Chemistry; Physical Chemistry; Physics
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APA (6th Edition):
Nelson, D. J. (2017). Photoelectron Spectroscopy of Organic Aromatic Anions. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/235
Chicago Manual of Style (16th Edition):
Nelson, Daniel John. “Photoelectron Spectroscopy of Organic Aromatic Anions.” 2017. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/chem_gradetds/235.
MLA Handbook (7th Edition):
Nelson, Daniel John. “Photoelectron Spectroscopy of Organic Aromatic Anions.” 2017. Web. 28 Nov 2020.
Vancouver:
Nelson DJ. Photoelectron Spectroscopy of Organic Aromatic Anions. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/chem_gradetds/235.
Council of Science Editors:
Nelson DJ. Photoelectron Spectroscopy of Organic Aromatic Anions. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/chem_gradetds/235
University of Colorado
16.
Knurr, Benjamin James.
Structures and Charge Distributions of Cluster Anions Studied by Infrared Photodissociation Spectroscopy.
Degree: PhD, Chemistry & Biochemistry, 2014, University of Colorado
URL: https://scholar.colorado.edu/chem_gradetds/139
► Anions are relevant in many different facets of chemistry. The study of anions, their interaction with other atoms and molecules and the effect of…
(more)
▼ Anions are relevant in many different facets of chemistry. The study of anions, their interaction with other atoms and molecules and the effect of solvation on those interactions are of interest to further the understanding of chemical processes. Studies on cluster ions
in vacuo allow for the generation of and excellent control over chemically interesting species. Experiments of this nature are ideal for studying the fundamental interactions of molecular partners by eliminating many of the complications of obtaining spectroscopic data on an individual species in the condensed phase. The clusters studied can also be viewed as model systems for more complex chemical processes that are otherwise difficult to understand at a molecular level.
In one part of this work, infrared spectra were obtained for [M(CO
2)
n]
- (M = Au, Ag, Co, Ni and Cu) clusters. These studies were performed in an effort to understand the interactions resulting in the reduction of CO
2. These cluster systems are viewed as model single atom catalysts for the purpose of CO
2 reduction. Au, Ag and Cu were all found to form η
1 (monodentate) [MCO
2]
- complexes of the metal and one CO
2 molecule with a structure akin to the formate anion. Study of the solvation environment of these η
1 complexes reveals that the excess charge on the core can be polarized onto the CO
2 moiety with increasing efficiency from Au to Cu. Co, Ni and Cu all exhibit core ions of the form [CO
2MCO
2]
- where the CO
2 ligands are bound in a bidentate (η
2) fashion. The polarizability of the core species increases from Co to Cu. Cu is a member of both the first row transition metals and the coinage metals, and it shows interaction motifs characteristic of both groups of metals. Additionally, two studies were performed on [CoO(CO
2)
n]
- and [NiO(CO
2)
n]
- clusters. It is shown that similar core structures are present in both CoO and NiO clusters and that the general behavior of the clusters is comparable to the analogous non-oxide clusters.
Two studies were performed on non-metal containing systems. A charge transfer reaction between a nitromethane anion and iodomethane was vibrationally induced. It is found that vibrational excitation of C-H stretches on either of the species in the complex leads to charge transfer from the nitomethane to the iodomethane and results in the formation of I
- product anions. Ar tagging is used to study the energetics of the reaction and achieve quenching of the reactive channel. The reaction is discussed in the framework of a vibrationally induced S
N2 reaction.
The infrared spectra of a naphthalene anion clustered with one to six water molecules were measured. The π-system of the naphthalene accommodates the excess electron with a network of water molecules evolving on one side…
Advisors/Committee Members: Jorg M. Weber, Veronica M. Bierbaum, Henry Kapteyn, Heather Lewandowski, Carl Lineberger.
Subjects/Keywords: Anions; Carbon Dioxide; Clusters; Infrared; Spectroscopy; Vibrations; Chemistry; Physical Chemistry
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APA (6th Edition):
Knurr, B. J. (2014). Structures and Charge Distributions of Cluster Anions Studied by Infrared Photodissociation Spectroscopy. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/chem_gradetds/139
Chicago Manual of Style (16th Edition):
Knurr, Benjamin James. “Structures and Charge Distributions of Cluster Anions Studied by Infrared Photodissociation Spectroscopy.” 2014. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/chem_gradetds/139.
MLA Handbook (7th Edition):
Knurr, Benjamin James. “Structures and Charge Distributions of Cluster Anions Studied by Infrared Photodissociation Spectroscopy.” 2014. Web. 28 Nov 2020.
Vancouver:
Knurr BJ. Structures and Charge Distributions of Cluster Anions Studied by Infrared Photodissociation Spectroscopy. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/chem_gradetds/139.
Council of Science Editors:
Knurr BJ. Structures and Charge Distributions of Cluster Anions Studied by Infrared Photodissociation Spectroscopy. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/chem_gradetds/139
University of Colorado
17.
Yeo, Eng Hiang Mark.
The Laser Cooling and Magneto-Optical Trapping of the YO Molecule.
Degree: PhD, Physics, 2015, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/142
► Laser cooling and magneto-optical trapping of neutral atoms has revolutionized the field of atomic physics by providing an elegant and efficient method to produce…
(more)
▼ Laser cooling and magneto-optical trapping of neutral atoms has revolutionized the field of atomic physics by providing an elegant and efficient method to produce cold dense samples of ultracold atoms. Molecules, with their strong anisotropic dipolar interaction promises to unlock even richer phenomenon. However, due to their additional vibrational and rotational degrees of freedom, laser cooling techniques have only been extended to a small set of diatomic molecules.
In this thesis, we demonstrate the first magneto-optical trapping of a diatomic molecule using a quasi-cycling transition and an oscillating quadrupole magnetic field. The transverse temperature of a cryogenically produced YO beam was reduced from 25 mK to 10 mK via doppler cooling and further reduced to 2 mK with the addition of magneto-optical trapping forces.
The optical cycling in YO is complicated by the presence of an intermediate electronic state, as decays through this state lead to optical pumping into dark rotational states. Thus, we also demonstrate the mixing of rotational states in the ground electronic state using microwave radiation. This technique greatly enhances optical cycling, leading to a factor of 4 increase in the YO beam fluorescence and is used in conjunction with a frequency modulated and chirped continuous wave laser to longitudinally slow the YO beam. We generate YO molecules below 10 m/s that are directly loadable into a three-dimensional magneto-optical trap. This mixing technique provides an alternative to maintaining rotational closure and should extend laser cooling to a larger set of molecules.
Advisors/Committee Members: Jun Ye, Deborah S. Jin, John L. Bohn, Heather Lewandowski, Carl Lineberger.
Subjects/Keywords: Cryogenics; Frequency Combs; Mechanical effects of light on atoms; molecules; and ions; Slowing and cooling of molecules; Trapping of molecules; Optics; Quantum Physics
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Manager
APA (6th Edition):
Yeo, E. H. M. (2015). The Laser Cooling and Magneto-Optical Trapping of the YO Molecule. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/142
Chicago Manual of Style (16th Edition):
Yeo, Eng Hiang Mark. “The Laser Cooling and Magneto-Optical Trapping of the YO Molecule.” 2015. Doctoral Dissertation, University of Colorado. Accessed November 28, 2020.
https://scholar.colorado.edu/phys_gradetds/142.
MLA Handbook (7th Edition):
Yeo, Eng Hiang Mark. “The Laser Cooling and Magneto-Optical Trapping of the YO Molecule.” 2015. Web. 28 Nov 2020.
Vancouver:
Yeo EHM. The Laser Cooling and Magneto-Optical Trapping of the YO Molecule. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2020 Nov 28].
Available from: https://scholar.colorado.edu/phys_gradetds/142.
Council of Science Editors:
Yeo EHM. The Laser Cooling and Magneto-Optical Trapping of the YO Molecule. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/phys_gradetds/142
. 
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