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EVAPORATIVE ATTACHMENT OF SLOW ELECTRONS
TO FREE SODIUM CLUSTERS
by
Roman Mikhailovich Rabinovich
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
(PHYSICS)
May 2008
Copyright 2008 Roman Mihailovich Rabinovich
i
Object Description
| Title | Evaporative attachment of slow electrons to free sodium clusters |
| Author | Rabinovich, Roman Mikhailovich |
| Author email | rrabinov@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Physics |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2008-03-24 |
| Date submitted | 2008 |
| Restricted until | Unrestricted |
| Date published | 2008-04-15 |
| Advisor (committee chair) | Kresin, Vitaly |
| Advisor (committee member) |
Haas, Stephan Chang, Tu-nan Thompson, Richard Vilesov, Andrey |
| Abstract | We have carried out a measurement of the mass spectra of sodium cluster anions formed in the collisions of free neutral sodium clusters with beam of low energy (0.1 eV) electrons. Anions covering the size ranges from Na-7 to Na-92 and from Na-132 to Na-144 were observed. The anion mass spectra were recorded simultaneously with those of the precursor cluster beam, which allowed us to monitor the effect of electron capture on the relative abundances of various cluster sizes. The anion mass spectra demonstrated significant restructuring with respect to the precursor beam: a downshift of the shell-closing magic numbers, a change in the shape of the overall intensity envelope, and, significantly, an alteration in the relative intensities of the open-shell peaks located between the magic numbers. This alteration did not represent a simple pattern shift by one electron number, and required an accurate analysis.; The restructuring of the mass spectra was treated theoretically by means of an evaporative attachment model, consisting of three steps: (a) electron capture by the strong polarization potential of the cluster, (b) rapid dissipation of the electron energy into the internal vibrational energy of the cluster (cluster heating), and a statistical evaporative cooling process (monomer and dimer evaporations). The analysis yielded results in good agreement with the experimental data and explained the fine structure of the observed abundance restructuring patterns.; Based on an accurate statistical description of dimer evaporation we derived an adjustment to the previous literature values of sodium cluster dimer evaporation energies, which had been obtained from cluster photodissociation experiments. The exponential sensitivity of the evaporation process to the cluster evaporation energies allowed us to verify the validity of this adjustment. The corrected evaporation energies for dimers were found to be approximately 20% higher than the original values.; The results demonstrate that slow-electron capture offers a useful window into the statistical and binding properties of metal clusters. Conversely, they show that in interpreting electron capture and transfer reactions it is essential to account for the accompanying fragmentation effects. |
| Keyword | alkali clusters; electron attachment; evaporative attachment; evaporative cooling; evaporative ensemble |
| 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 |
| Type | texts |
| Legacy record ID | usctheses-m1112 |
| Rights | Rabinovich, Roman Mikhailovich |
| 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-Rabinovich-20080415 |
| Archival file | uscthesesreloadpub_Volume17/etd-Rabinovich-20080415.pdf |
Description
| Title | Page 1 |
| Full text | EVAPORATIVE ATTACHMENT OF SLOW ELECTRONS TO FREE SODIUM CLUSTERS by Roman Mikhailovich Rabinovich 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 (PHYSICS) May 2008 Copyright 2008 Roman Mihailovich Rabinovich i |
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