Pressure broadening and pressure shift of diatomic iodine at 675 nm
| dc.contributor.author | Wolf, Erich N. | |
| dc.date.accessioned | 2010-03-12T01:51:07Z | |
| dc.date.available | 2010-03-12T01:51:07Z | |
| dc.date.issued | 2009-06 | |
| dc.description | xvi, 280 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. | en_US |
| dc.description.abstract | Doppler-limited, steady-state, linear absorption spectra of 127 I 2 (diatomic iodine) near 675 nm were recorded with an internally-referenced wavelength modulation spectrometer, built around a free-running diode laser using phase-sensitive detection, and capable of exceeding the signal-to-noise limit imposed by the 12-bit data acquisition system. Observed I 2 lines were accounted for by published spectroscopic constants. Pressure broadening and pressure shift coefficients were determined respectively from the line-widths and line-center shifts as a function of buffer gas pressure, which were determined from nonlinear regression analysis of observed line shapes against a Gaussian-Lorentzian convolution line shape model. This model included a linear superposition of the I 2 hyperfine structure based on changes in the nuclear electric quadrupole coupling constant. Room temperature (292 K) values of these coefficients were determined for six unblended I 2 lines in the region 14,817.95 to 14,819.45 cm -1 for each of the following buffer gases: the atoms He, Ne, Ar, Kr, and Xe; and the molecules H 2 , D 2 , N 2 , CO 2 , N 2 O, air, and H 2 O. These coefficients were also determined at one additional temperature (388 K) for He and CO 2 , and at two additional temperatures (348 and 388 K) for Ar. Elastic collision cross-sections were determined for all pressure broadening coefficients in this region. Room temperature values of these coefficients were also determined for several low- J I 2 lines in the region 14,946.17 to 14,850.29 cm -1 for Ar. A line shape model, obtained from a first-order perturbation solution of the time-dependent Schrödinger equation for randomly occurring interactions between a two-level system and a buffer gas treated as step-function potentials, reveals a relationship between the ratio of pressure broadening to pressure shift coefficients and a change in the wave function phase-factor, interpreted as reflecting the "cause and effect" of state-changing events in the microscopic domain. Collision cross-sections determined from this model are interpreted as reflecting the inelastic nature of collision-induced state-changing events. A steady-state kinetic model for the two-level system compatible with the Beer-Lambert law reveals thermodynamic constraints on the ensemble-average state-changing rates and collision cross-sections, and leads to the proposal of a relationship between observed asymmetric line shapes and irreversibility in the microscopic domain. | en_US |
| dc.description.sponsorship | Committee in charge: David Herrick, Chairperson, Chemistry; John Hardwick, Advisor, Chemistry; Jeffrey Cina, Member, Chemistry; David Tyler, Member, Chemistry; Michael Raymer, Outside Member, Physics | en_US |
| dc.identifier.uri | https://hdl.handle.net/1794/10267 | |
| dc.language.iso | en_US | en_US |
| dc.publisher | University of Oregon | en_US |
| dc.relation.ispartofseries | University of Oregon theses, Dept. of Chemistry, Ph. D., 2009; | |
| dc.subject | Pressure broadening | en_US |
| dc.subject | Pressure shift | en_US |
| dc.subject | Diatomic iodine | en_US |
| dc.subject | Line shape | en_US |
| dc.subject | Elastic collisions | en_US |
| dc.subject | Physical chemistry | en_US |
| dc.subject | Optics | en_US |
| dc.subject | Theoretical physics | en_US |
| dc.title | Pressure broadening and pressure shift of diatomic iodine at 675 nm | en_US |
| dc.type | Thesis | en_US |
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