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PHOTOELECTRON AND ION IMAGING INVESTIGATIONS OF
SPECTROSCOPY, PHOTOIONIZATION, AND PHOTODISSOCIATION
DYNAMICS OF DIAZOMETHANE AND DIAZIRINE
by
Igor Fedorov
___________________________________________________________________
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMISTRY)
August 2009
Copyright 2009 Igor Fedorov
Object Description
| Title | Photoelectron and ion imaging investigations of spectroscopy, photoionization, and photodissociation dynamics of diazomethane and diazirine |
| Author | Fedorov, Igor |
| Author email | fedorov@usc.edu; fedorov.rus@gmail.com |
| Degree | Doctor of Pharmacy / Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemistry (Chemical Physics) |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2009-06-05 |
| Date submitted | 2009 |
| Restricted until | Unrestricted |
| Date published | 2009-07-02 |
| Advisor (committee chair) | Reisler, Hanna |
| Advisor (committee member) |
Gruntman, Mike Krylov, Anna I. |
| Abstract | The photophysics and photochemistry of two isomers of CH(subscript 2)N(subscript 2), diazomethane and diazirine, was studied in molecular beam. Their pyrolysis was used to produce molecular beam of methylene radicals in the ground electronic state. The spectroscopy, photoionization, and photodissociation pathways of diazomethane and diazirine were investigated experimentally using a combination of 2 + 1 REMPI and velocity map imaging techniques. For three isotopologs of diazomethane, the 2(superscript 1)A(subscript 2)(3p(subscript y) ← π) and 2(superscript 1)B(subscript 1)(3p(subscript z) ← π) Rydberg states are of mostly pure Rydberg character, whereas the 3(superscript 1)A(subscript 1)(3p(subscript x) ← π) state is mixed with the valence 2(superscript 1)A(subscript 1)(π*← π) state. Normal mode vibrational frequencies were obtained for the 2(superscript 1)A(subscript 2)(3p(subscript y)) Rydberg state and cation, and mixed levels of the 2(superscript 1)A(subscript 2)(3p(subscript y)) and 2(superscript 1)B(subscript 1)(3p(subscript z)) states of the three isotopologs were identified. The agreement between experiment and theory was very good allowing a full analysis of trends in structure and vibrational frequencies going from the neutral species to the excited Rydberg state, and the cation. In the experiments with diazirine, the weak one-photon absorption to the 1(superscript 1)B(subscript 2) state is immediately followed by more efficient absorption of another photon to reach the 1(superscript 1)A(subscript 2) state from which competition between ionization and fast dissociation takes place. Strong signals of CH+ ions are also detected and assigned to 2 + 1 REMPI of CH fragments. Velocity map CH(superscript +) images show that CH (X, v"=0, N") fragments are born with substantial translational energy indicating that they arise from absorption of two photons in diazirine.; It is argued that two photon processes via the 1(superscript 1)B(subscript 2) intermediate state are very efficient in 304–325 nm wavelength range, leading predominantly to dissociation of diazirine from the 1(superscript 1)A(subscript 2) state. The most likely route to CH(X) formation is isomerization to isodiazirine followed by dissociation to CH + HN( subscript 2). We recommend revisions of the heats of formation of diazomethane and diazirine to 67 ± 3 and 77 ± 3 kcal/mol, respectively. CH2 radicals were produced at high concentration with low contamination in a molecular beam by pyrolysis of diazomethane and diazirine in a home-built pulsed pyrolysis source. The (superscript 3)CH( subscript 2) radicals were detected by 2 + 1 REMPI via the 3p Rydberg state. |
| Keyword | diazomethane; diazirine; methylene; imaging; pyrolysis; resonance enhanced multiphoton ionization; spectroscopy; photodissociation dynamics; photoionization |
| 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-m2322 |
| Rights | Fedorov, Igor |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Fedorov-3025 |
| Archival file | uscthesesreloadpub_Volume48/etd-Fedorov-3025.pdf |
Description
| Title | Page 1 |
| Full text | PHOTOELECTRON AND ION IMAGING INVESTIGATIONS OF SPECTROSCOPY, PHOTOIONIZATION, AND PHOTODISSOCIATION DYNAMICS OF DIAZOMETHANE AND DIAZIRINE by Igor Fedorov ___________________________________________________________________ A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (CHEMISTRY) August 2009 Copyright 2009 Igor Fedorov |
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