Date of Award

2019

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Physics

Keywords

Electron collisions, Metastable atoms, Rare gas matrices

Supervisor

John McConkey

Rights

info:eu-repo/semantics/openAccess

Abstract

Measurements of the production of atomic and molecular metastable states are performed using a novel frozen solid layer detector. This includes examination of solid CO2 and N2O layers in metastable detection, measurements of N(2P) production from dissociation of N2, investigations into the suitability of solid neon layers for detection of S(1D) based on electron-impact dissociation studies of OCS and production of O(1S) and CO(a3Pi) in electron-impact dissociation of methanol. Novel solid layers for detection of metastable states were examined to determine which products they were sensitive to. First, CO2 layers were deposited and were found to be sensitive to both O(1S) and N2(a1Pi g) metastable states. The relative efficiency of these layers as a function of temperature and lifetime of the state formed from the impinging O(1S) atoms are reported. Mechanisms which may be responsible for the radiation through formation of CO3 or its ion are also suggested. The detection of metastable N2(a1Pi g) states from solid N2O layers is also reported. A study of N(2P) production after electron-impact dissociation of N2 was also performed. It was determined that two excitation channels contribute to production of this state. Time-of-flight and fragment kinetic energy spectra are presented for 100 eV impact energy. Excitation function data is also provided over the 0-200 eV range for one of these channels. Dissociation processes are proposed for both production channels which appear to be due to both a direct dissociation and pre-dissociation mechanism. Intermediary states are proposed for both channels. Investigations into the suitability of solid neon layers for the detection of S(1D) are performed through studies of electron-impact dissociation of OCS. It was found that while production of S(1D) is likely occurring, interactions with solid neon layers do not result in emission within the optical spectral range of our photo-multiplier tube. However, an ultraviolet emission from these layers was detected in these experiments. While the nature of this feature was not definitively identified, some possible processes which may be responsible are discussed. Future investigations to determine the source of the emission are proposed. In addition, likely production channels of S(1D) are suggested. Electron-impact dissociation of methanol was also performed. It was observed that both CO(a3Pi) and O(1S) metastable states are produced and detected with solid xenon layers. While production of CO(a3Pi) has been reported previously, this appears to be the first observation of O(1S) production from electron-impact of methanol. Time-of-flight and released kinetic energy spectra are presented for both features at 100 eV impact energy. Excitation functions are also presented for 10-90 eV impact energy for both states. The production of CO(a3Pi) coincides with the observations of previous studies and the measurement of the excitation cross section is extended from an energy of 21 to 90 eV. No new dissociation channels for this state were found. Meanwhile, production of O(1S) appears to occur through a direct dissociation mechanism causing breakage of the CO bond and formation of OH(B2Sigma-) which subsequently dissociates into O(1S) and H(2S).

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