Doctoral Dissertations

Date of Award

5-1991

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Robert N. Compton

Abstract

Collisional relaxation of the 6s[3/2]1, 6s'[1/2]1, 5d[3/2]1, and the 7s[3/2]1 mj levels of xenon has been investigated experimentally. Disalignment and dephasing of the mj levels have been studied by measuring the pressure dependence of the ratio of the ionization from selectively excited mj=0 and mj±1 sublevels in a three photon resonant ionization experiment employing novel use of two counterpropagating beams with parallel and perpendicular polarizations, respectively. Angular distributions for energy resolved photoemitted electrons from resonantly enhanced multiphoton ionization (REMPI) via the two-photon allowed, (2+1), 6p[1/2]0, 6p[3/2]2, 6p'[1/2]0, 6p'[3/2]2, 7p[1/2]0, 7p[3/2]2, and 7p[5/2]2 states, and the three-photon allowed, (3+1), 7s[3/2]1, 8s[3/2]1, 9s[3/2]1, 5d[3/2]1, 5d'[5/2]3, and 5d'[3/2]1 states of xenon and the three-photon allowed, (3+2), 5s[3/2]1, and the (3+1) 6s[3/2]1, 4d[3/2]1, 4d[5/2]3, and 4d[7/2]3 states of krypton are reported. The measured angular distributions are compared to theoretically generated curves based on multichannel quantum defect theory (MQDT). Photoelectron energy and angular distributions for the REMPI process via the four-photon allowed, (4+1), 6p[1/2]0 and 6p[3/2]2 states of xenon are also reported. Photoelectrons due to above threshold ionization, (4+2), resonantly enhanced via the four-photon allowed 6p[1/2]0 state are also observed. Photoelectron energy distributions are also reported for resonantly enhanced multiphoton ionization via a number of two- and three-photon allowed transitions in ethylene and trans-1,3-butadiene. In addition, a detailed description of a double reflectron mass spectrometer is also given. Energy resolved angular distributions are reported for resonantly enhanced multiphoton ionization via the two-photon allowed C 2II state of ArNO. Multiphoton excitation and ionization processes in dense (1-10 Torr) lithium, potassium, and sodium vapor was also studied. A number of different nonlinear processes were observed and reported including self focussing, stimulated electronic Raman scattering (SERS), stimulated hyper-Raman scattering (SHRS), and various four and six wave-mixing processes. Some of the more interesting processes studied involved hybrid resonances, conical emission, and third harmonic generation in sodium vapor.

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