Electronic spectroscopy of rare -gas sulfhydryl and hydroxyl complexes

Rare-gas-open-shell complexes provide a unique opportunity to study weak interactions. In particular, a series of rare-gas (Rg) sulfhydryl complexes along with an additional Rg-hydroxyl complex have been studied, along with their deuterated analogs; these include Ne·SH/D, Ar·SH/D, Kr·SH/D, and Kr·OH/D. Electronic spectra have been taken of all these species. This includes both vibronically resolved and rotationally resolved spectra of the A&d15;S+ 2 ↔ X&d15;P 2 electronic transition.;The transition observed in all these species originates from a very weakly bound ground state. The characteristics of the ground state are largely independent of which of the rare gases and diatomic moiety is involved. However, upon excitation to the A&d15;S+ 2 state, a significant shortening of the bond is observed and the bond strength can vary from a weakly bound nearly free rotor to a quite strongly bound almost semi-rigid bender.;The theory involved for both the vibronic and rotational analysis is presented. The different types of transitions, the resulting different angular momenta coupling, the interactions involved and their effects on the spectra are discussed. The parameters resulting from the analyses are presented along with representative spectra of the various transitions observed with these complexes.;From the experimentally determined rotational constants along with the measured vibrational energy levels are used to develop empirical potential energy surfaces (PES) for all of the complexes noted above as well as those for the Ne·OH/D and Ar·OH/D species to provide a full picture of this very interesting large family of complexes. Along with the PES themselves, plots of the absolute square of the wavefunction are superimposed upon the PES. This is done for a variety of vibronic levels depicting the area of the PES sampled by the experiment.;From the results of the experimental analyses and the resulting PES there are certain trends found in this large group of complexes. The bonding exhibited in the A&d15;S+ 2 state, within each diatom species, increases with increasing rare-gas atom size. Additionally, the bond strength of the hydroxyl species is greater than that found in the sulfhydryl species with the same rare gas atom. This and other trends are discussed.