Date of Award

1993

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Physics

First Advisor

McConkey, John William,

Keywords

Physics, Molecular.

Rights

CC BY-NC-ND 4.0

Abstract

The metastable species O($\sp1$S) has been observed following the dissociation of O$\sb2$, N$\sb2$O, and CO$\sb2$ molecules by pulsed electron impact. A crossed beam apparatus was used to obtain time-of-flight spectra of the fragments. A novel detector which consists of a layer of freshly deposited Xe was employed. O($\sp1$S) atoms impinging on the surface quickly (${\sim}$1$\mu$s) form XeO* excimers which rapidly decay (${\sim}$100ns) producing easily detected photons. In the case of O$\sb2$ and N$\sb2$O present results indicate that this method is sensitive solely to O($\sp1$S) with high quantum efficiency. Other ground state or metastable fragments (such as O($\sp3$P), O($\sp1$D), O($\sp5$S$\sp{\rm o}$), or N$\sb2$(A$\sp3\Sigma\sbsp{\rm u}{+}$)) have not been detected. In the case of CO$\sb2$, the Xe layer is sensitive to O($\sp1$S) and the metastable CO(a$\sp3\Pi$). Low resolution optical spectra of the emissions which follow the arrival of O($\sp1$S) at the Xe layer reveal bands at 375, 550, and 725 nm; while CO(a$\sp3\Pi$) fragments impinging on the layer produce emissions below 350 nm. Time-of-flight and released kinetic energy spectra for all target gases at various electron impact energies are presented together with excitation functions from threshold to 1000 eV. These have been made absolute using a Bethe-Born calibration technique for O($\sp1$S) from N$\sb2$O. For O($\sp1$S) from O$\sb2$ and CO$\sb2$, the data are calibrated relative to N$\sb2$O. Maximum cross sections for O($\sp1$S) production are 2.25 $\times$ 10$\sp{-17}$ cm$\sp2$ at 45 eV, 2.08 $\times$ 10$\sp{-18}$ cm$\sp2$ at 80 eV, and 1.68 $\times$ 10$\sp{-17}$ cm$\sp2$ at 50 eV, for N$\sb2$O, O$\sb2$, and CO$\sb2$ targets respectively. The cross section for CO(a$\sp3\Pi$) production from dissociative excitation of CO$\sb2$ has a maximum of 2.8 $\times$ 10$\sp{-16}$ cm$\sp2$ at 25 eV.Dept. of Physics. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1993 .L435. Source: Dissertation Abstracts International, Volume: 55-05, Section: B, page: 1893. Adviser: John William McConkey. Thesis (Ph.D.)--University of Windsor (Canada), 1993.

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