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Experimental studies of the excitation of metastable states in molecules by electron impact

Furlong, Joan Marion; (1993) Experimental studies of the excitation of metastable states in molecules by electron impact. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

This thesis presents four experimental investigations of forbidden transitions in small molecules, carried out using the technique of electron-scattering spectroscopy. These studies make use of a high-resolution electron spectrometer capable of resolving narrow resonance features in the excitation cross sections of metastable species. In the first investigation, a new low-work-function surface detector is designed in order to increase the detection efficiency for metastable species. Four types of detector surface material are evaluated: lead-silicate glass, copper-beryllium, hafnium and a triple-oxide compound of barium, strontium and calcium. The relative detection efficiencies of these surfaces are shown to vary with the species of metastable examined. The second investigation is a study of the decay of core-excited Feshbach resonances into the metastable c3II-u state of H2, HD and D2. Metastable excitation cross sections are measured in the 11-13eV energy range for these three isotopes. The vibrational separations of two resonance series observed in the cross section are shown to be isotope- dependent. In the third investigation, integral cross section measurements in the energy range 6-70 eV are carried out for the metastable a3II state in CO by making use of the time-of-flight technique. A critical review of previous experimental and theoretical determinations of the excitation cross section of a '10 eV' metastable species in CO is presented. Finally, the fourth investigation is a search for metastable species in NO and C2H2, making use of a new, high-current electron gun specifically designed to facilitate their detection.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Experimental studies of the excitation of metastable states in molecules by electron impact
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Pure sciences; Applied sciences; Electron impact; Excitation of metastable; Molecules
URI: https://discovery.ucl.ac.uk/id/eprint/10097620
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