Single- and Multiphoton Ionization Processes in Molecules

Author: Dubs, Richard Leslie

Year: 1988

Degree: Dissertation (Ph.D.)

Advisor: McKoy, Basil Vincent

Committee Members: Kuppermann, Aron; McKoy, Basil Vincent; Dougherty, Dennis A.; Weitekamp, Daniel P.

Option: Chemistry

DOI: 10.7907/63a3-d438

Abstract

This dissertation is theoretical in nature and can be separated into two main areas: 1) single- and multiphoton ionization studies of a novel photoelectron effect, and 2) single-photon ionization studies of simple clusters as models for adsorbate photoemission. The first area centers on the phenomenon of circular dichroism in photoelectron angular distributions (CDAD). CDAD is shown to exist from oriented linear molecules, adsorbed atoms, and aligned atoms and molecules in the gas phase. The calculations presented here are the first to demonstrate the experimental feasability of CDAD studies. CDAD is shown to be a measurable effect which exists because the photoelectron collection direction can break the symmetry of these otherwise highly symmetric systems. As a direct result of the work presented here, CDAD has now been observed experimentally. Coupled with resonantly enhanced multiphoton ionization (REMPI), CDAD is shown to be a powerful probe of unknown alignment in gas phase atomic and molecular samples. The second area of research focuses on the simple oriented molecules NiCO and NiN₂ as models for the corresponding adsorbate systems. These simple models provide insight into features observed in the experimental angle-resolved photoemission spectra.

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