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iii
Acknowledgments
I would first like to thank my scientific advisor, Professor Andrey Vilesov, for his
constant support during my graduate career at USC. He has a comprehensive
experimental repertoire of knowledge that he has always been willing to share with me.
As a result, I attribute most of my success as a scientist to him. In addition, his office has
always been open to discuss not only science but life in general and I have been very
fortunate to have worked in his group.
I am also very grateful to Professor Hanna Reisler for her constant support and
attention she has provided me over the years while at USC. Her interest in the success of
students outside her own research group is sincere and inspirational. I would also like to
thank the remaining members of my qualifying exam committee, Professor Vitaly Kresin,
Professor Chi Mak, and Professor Thomas Flood, for their support. In addition, I would
like to thank Professor Curt Wittig for his wisdom and always strong personality.
I would like to thank Professor Stephen Bradforth and Professor Susumu
Takahashi for their support while a T.A. for CHEM 332L. Many problems in the lab
would not have been fixed if not for their advice and guidance. In addition, I would like
to thank Jaime Avila, the department computer consultant, for his assistance in the lab.
When I first joined the Vilesov group, I was slightly overwhelmed. Fortunately,
veteran graduate students Kirill Kuyanov and Dmitry Skvortsov were there to show me
the ropes in the laboratory. As a result, I would like to thank them for all of their help.
Although he was not at USC for very long, I would like to thank our previous post-doc
Object Description
| Title | Infrared and Raman spectrosopy of molecules and molecular aggregates in helium droplets |
| Author | Sliter, Russell Thomas |
| Author email | sliter@usc.edu; sliterr@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemistry |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2011-04-21 |
| Date submitted | 2011 |
| Restricted until | Unrestricted |
| Date published | 2011-04-26 |
| Advisor (committee chair) | Vilesov, Andrey F. |
| Advisor (committee member) |
Reisler, Hannah Kresin, Vitaly V. |
| Abstract | This dissertation covers several different aspects of spectroscopy of molecules and molecular clusters embedded in low-temperature matrices, such as helium droplets. First, details on the formation and optimization of He droplets will be discussed. A new method of measuring droplet sizes for cw nozzle expansions using mass spectrometry was developed. The results of the measurements of the sizes of the droplets in pulsed expansion as a function of temperature will be described. Details on the electron-impact ionization of He droplets will also be discussed as well as a simple method of modeling the ionization and excitation of He atoms in the droplet. In addition, preliminary measurements on the size distribution of He droplets produced at very low temperature of 5 – 7 K in continuous expansion will be addressed.; Using matrix isolation in He droplets, vibrational spectra of clusters consisting of para-H₂ or para-H₂/D₂ have been obtained using coherent anti-Stokes Raman spectroscopy (CARS). The vibrational frequency of para-H₂ molecules obtained upon expansion of neat para-H₂/D₂ gas or liquid was found to be very similar to that in bulk solid samples having equal composition. On the other hand, spectra in clusters obtained upon expansion of 1% para-H₂/D₂ clusters seeded in He are liquid and have a considerable frequency shift, which indicate phase separation of the two isotopes in clusters at low temperature. The onset of phase separation in para-H₂/D₂ mixtures is predicted at approximately 3 K providing further evidence of super-cooled liquid hydrogen clusters.; To address the Raman spectra observed in liquid H2 clusters, vibrational and rotational spectra of bulk liquid para-H2 at temperature of T = 14 – 26 K and of solid at T = 6 – 13 K have been obtained using coherent anti-Stokes Raman scattering technique. The vibrational frequency in the liquid increases with temperature by about 2 cm⁻¹, and the shift scales with the square of the sample’s density. An extrapolation of the vibrational frequency in the metastable para-H₂ liquid below the freezing point is discussed. The results indicate that the vibron hopping between the molecules is active in the liquid, similar to that previously found in the solid.; Matrix isolation has also been performed in argon solid matrices based on a custom-made cryogenic optical cell. Single water molecules have been isolated in solid Ar matrices at 4 K and studied by ro-vibrational spectroscopy using FTIR in the regions of the v₁, v₂, and v₃ modes. Upon nuclear spin conversion at 4 K, essentially pure para-H₂O was prepared followed by subsequent fast annealing generating ice particles. FTIR studies of the vapor above the condensed water upon annealing to T ≥ 250 K indicate fast re-conversion of nuclear spin to equilibrium conditions. Our results indicate that nuclear spin conversion is fast in water dimers and larger clusters, which preclude preparation of concentrated samples of para-H₂O, such as in ice or vapor. |
| Keyword | Helium droplets; laser spectroscopy; matrix isolation; superfluidity; clusters |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m3778 |
| Contributing entity | University of Southern California |
| Rights | Sliter, Russell Thomas |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Sliter-4404 |
| Archival file | uscthesesreloadpub_Volume23/etd-Sliter-4404.pdf |
Description
| Title | Page 3 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | iii Acknowledgments I would first like to thank my scientific advisor, Professor Andrey Vilesov, for his constant support during my graduate career at USC. He has a comprehensive experimental repertoire of knowledge that he has always been willing to share with me. As a result, I attribute most of my success as a scientist to him. In addition, his office has always been open to discuss not only science but life in general and I have been very fortunate to have worked in his group. I am also very grateful to Professor Hanna Reisler for her constant support and attention she has provided me over the years while at USC. Her interest in the success of students outside her own research group is sincere and inspirational. I would also like to thank the remaining members of my qualifying exam committee, Professor Vitaly Kresin, Professor Chi Mak, and Professor Thomas Flood, for their support. In addition, I would like to thank Professor Curt Wittig for his wisdom and always strong personality. I would like to thank Professor Stephen Bradforth and Professor Susumu Takahashi for their support while a T.A. for CHEM 332L. Many problems in the lab would not have been fixed if not for their advice and guidance. In addition, I would like to thank Jaime Avila, the department computer consultant, for his assistance in the lab. When I first joined the Vilesov group, I was slightly overwhelmed. Fortunately, veteran graduate students Kirill Kuyanov and Dmitry Skvortsov were there to show me the ropes in the laboratory. As a result, I would like to thank them for all of their help. Although he was not at USC for very long, I would like to thank our previous post-doc |
