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Title: Applications of high-resolution translational spectroscopy
Author: Enos, C. S.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1993
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In 1927, E.P. Wigner proposed that in the event of weak spin-orbit coupling the only spectroscopic processes likely to occur were those for which the total electron spin angular momentum was conserved, namely ΔS = 0. This later became known as the Wigner Spin Conservation Rule. Its implications for radiative processes have been extensively investigated and it is now known that they adhere closely to the ΔS = 0 selection rule. In contrast, the application of the spin rule to binary collisional processes has been the subject of a small number of studies from which only tentative conclusions could be drawn as to its validity. To redress this imbalance, a systematic investigation was undertaken by the author for ion (keV)-particle (thermal) collisions, the results of which are presented in this thesis. In total, 164 reaction channels were identified of which the overwhelming majority (158) were found to be spin conservative. Furthermore, a modified version of the ΔS = 0 selection rule is proposed which states that if one collision partner undergoes a transition involving a multiplicity change a simultaneous transition in the other partner must conform to the selection rule ΔS = 0 or 1 with the proviso that singlet-singlet transitions are forbidden. During a charge stripping investigation of 4keV B^+,C^+ and Ar^+ ions, several features observed in the spectra using non-singlet target particles such as O_2 and NO, were not present when singlet target particles such as N_2 and Ne were used. To explain these discrepancies, a novel pseudo two step mechanism is proposed in which the ion undergoes a rearrangement stage prior to explusion of the electron. Metastable ions substantially influence collisional processes and to facilitate the former investigations, the fractional metastable content of six atomic ion beams (B^+, C^+, N^+, O^+, F^+ and Cl^+) formed by Electron Ionization are quantified.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available