Date of Award
1996
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
The {dollar}\rm B\sp2\Sigma\sp{lcub}+{rcub}{dollar} ion-pair excited states for the unstable group IIB metal monohalide radicals have acquired eminence as the upper levels for the potentially important blue/green lasers. In this work, the metal monohalide radicals were produced by exciting a corona excited electrical discharge in a supersonic gas expansion. The ion-pair-valence {dollar}\rm B\sp2\Sigma\sp{lcub}+{rcub}\gets X\sp2\Sigma\sp{lcub}+{rcub}{dollar} transitions for several of these species were recorded by the method of laser induced fluorescence excitation spectroscopy. For HgCl the resultant spectra recorded over the 368-267nm range reveal an extensive vibrationally and isotopically resolved structure due to transitions between {dollar}\rm X\sp2\Sigma\sp{lcub}+{rcub}\ (2\ge v\sp{lcub}\prime\prime{rcub}\ge0){dollar} and {dollar}\rm B\sp2\Sigma\sp{lcub}+{rcub}\ (75\ge v\sp\prime\ge21){dollar}. The {dollar}\rm B\sp2\Sigma\sp{lcub}+{rcub}\gets X\sp2\Sigma\sp{lcub}+{rcub}{dollar} fluorescence excitation spectrum for HgI extending from 322nm to 367nm shows that transitions from the lowest ground state levels {dollar}\rm (v\sp{lcub}\prime\prime{rcub}=0-2){dollar} excite the ion-pair state over a wide range of high vibrational levels {dollar}\rm (v\sp\prime=30-70).{dollar} The HgBr vibrational progressions {dollar}\rm B\sp2\Sigma\sp{lcub}+{rcub}(v\sp\prime=62-54)\gets X\sp2\Sigma\sp{lcub}+{rcub} (v\sp{lcub}\prime\prime{rcub}=0-1){dollar} were also recorded. Franck-Condon factor calculations were carried out to estimate the equilibrium bond lengths of the excited states.;High quality spectra for the heteronuclear rare gas excimers have long eluded experimentalists since these molecules are physically unstable. Recently, our group recorded single isotopomer resonantly enhanced {dollar}(2+1){dollar} multiphoton ionization spectra of jet cooled ArKr and NeXe using time-of-flight mass detection. In this thesis the findings of the vibrational analyses for several transitions of these two molecules are presented.;Excited state equilibrium bond lengths for all of the Rydberg states observed were estimated using Franck-Condon factor calculations. Four band systems of ArKr were observed in the energy region 94825-92012 cm{dollar}\sp{lcub}-1{rcub}{dollar} whose exerted states dissociate to {dollar}\rm Ar+Kr\sp{lcub}*{rcub}(5p){dollar} or{dollar}\rm Kr+Ar\sp{lcub}*{rcub}(4s){dollar}. Eight Rydberg state-ground state transitions of NeXe were identified whose upper states dissociate to {dollar}\rm Ne+Xe\sp{lcub}*{rcub}(6p{dollar} or 5d) in the region between 80073-78546 cm{dollar}\sp{lcub}-1{rcub}{dollar}. To aid in the electronic symmetry assignments all spectra were recorded separately with linearly and circularly polarized radiation. A model is presented to explain the trends of the excited states dissociation energies and vibrational frequencies in terms of the relative importance of covalent bonding versus long range interactions.
Recommended Citation
Bascal, Hafed Ashur, "Spectroscopy Of Unstable Molecules" (1996). Digitized Theses. 2606.
https://ir.lib.uwo.ca/digitizedtheses/2606