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
