| This dissertation includes three spectroscopic studies of transient molecules which are important in semiconductor growth processes or of environmental interest. Chapter I is an introduction to electronic and vibrational spectroscopy, and the background of ab initio calculations.; In Chapter II, we report that an extensive vibronic band system of the FS{dollar}sb2{dollar} radical in the 700-485 nm region has been observed for the first time by laser induced fluorescence probing of the products of the reaction of F{dollar}sb2{dollar} with various sulfur-containing compounds. Jet-cooled spectra were obtained by reacting fluorine with COS, H{dollar}sb2{dollar}S or CS{dollar}sb2{dollar} in the body of a continuous supersonic jet, just prior to expansion. Rotational analyses of the high resolution spectra of six vibronic bands show that the transition is polarized out-of-plane, with spin splittings characteristic of a molecule with a single unpaired electron. The rotational constants and spin-rotation interaction constants were determined with good precision for the ground and excited states.; In Chapter III, ab initio theory with split-valence plus polarization functions and larger basis sets at the SCF and UMP2 levels was used to predict the geometries and spectroscopic parameters for the ground and first excited electronic states of the HS{dollar}sb2,{dollar} FS{dollar}sb2{dollar} and ClS{dollar}sb2{dollar} free radicals. The ground state species are predicted to be bent and may be described as having a sulfur-sulfur double bond, a sulfur-substituent single bond and an unpaired electron which is delocalized principally over the sulfur centers.; In Chapter IV, spectra of jet-cooled germanium dichloride were obtained by pyrolysis of trichlorogermane in the throat of a supersonic jet. Laser-induced emission excitation spectra were recorded for the weak 450-400 nm and strong 320-300 nm band systems, both of which were vibrationally analyzed. Ab initio predictions of the excited state geometries, vibrational frequencies and excitation energy were made to aid in assigning the spectra.; In Chapter V, the high-resolution (0.002 cm{dollar}sp{lcub}-1{rcub}{dollar}) infrared spectrum of {dollar}nusb3{dollar} band of the transient molecule deuterated formyl chloride, DCOCl, is analyzed in detail. Assignments of A- and B-type lines of both DCO{dollar}sp{lcub}35{rcub}{dollar}Cl and DCO{dollar}sp{lcub}37{rcub}{dollar}Cl are made for this A/B hybrid band between 915 and 1059 cm{dollar}sp{lcub}-1{rcub}{dollar}. The excited state constants of both isotopomers have been obtained over a wide range of J and K{dollar}sb{lcub}rm a{rcub}{dollar} values. The {dollar}nusb3{dollar} band shows no evidence of excited state perturbations. (Abstract shortened by UMI.)... |
