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|Title:||Laser induced fluorescence spectroscopy and matrix isolation studies of the alkali oxides and other metal-containing free radicals|
|Authors:||Beardah, Alison Margaret.|
|Presented at:||University of Leicester|
|Abstract:||The work presented in this thesis is concerned with the preparation and study of simple metal-containing molecules, produced via laser ablation and studied using laser electronic spectroscopy. The results of attempted spectroscopic studies of both lithium and sodium monoxide are presented. The first observation of electronic spectra of the LiO free radical in a supersonic jet is reported. Using laser ablation of lithium in the presence of nitrous oxide, laser induced fluorescence (LIF) excitation spectra in the 30800-28200 cm"1 region have been observed and assigned to the C2II - X2II transition of LiO. The LIF excitation spectra show abundant structure and are much more complicated than generally expected for a simple diatomic molecule. Further experiments, where LiO was probed without jet cooling, saw the structure in the 30800-28200 cm'1 region disappear and a new excitation spectrum appear further to the red, in the 24390-23256 cm"1 region. From these findings it is deduced that the exothermic reaction between Li + N2O > LiO + N2 produces a population inversion in the LiO product, most likely an electronic state population inversion. The spectrum in the 24390-23256 cm"1 region was assigned to the C2II - A2E+ system. Attempts to probe LiO via stimulated emission pumping (SEP) spectroscopy are also reported. Following this initial work a new matrix isolation apparatus was built to allow the alkali oxides and many other metal-containing species to be investigated in cold inert matrices. The new experimental set-up allows metal-containing molecules to be generated via several techniques, including laser ablation, and probed via LIF excitation and dispersed fluorescence (DF) spectroscopy. Details of the design and development of the new experimental chamber, along with some preliminary results, are reported. Finally LIF excitation and dispersed fluorescence spectra of an unknown barium-containing species are presented. Arguments are presented which suggest that the excitation spectral carrier is most likely the Ba.OH2 adduct which, on electronic excitation, undergoes predissociation to either HBaO or HBaOH. Alternatively the band system may be due to the Ba 6s2 0 -> Ba 6s1 np1 !Pi Rydberg series.|
|Rights:||Copyright © the author. All rights reserved.|
|Appears in Collections:||Theses, Dept. of Chemistry|
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