A vacuum ultraviolet laser study of IBr

Abstract
Vacuum ultraviolet (VUV) fluorescence excitation spectra of jet-cooled IBr, between 173·6 and 163·5 nm, were recorded using tunable, laser-like VUV radiation generated by four-wave mixing in Mg vapour and Xe gas. An unambiguous vibrational analysis shows that transitions from υ″ = 0 of the ground state probe high vibrational levels of the first tier ion-pair state EO+ between υ′ = 260 and 383. Molecular constants derived from both Dunham and near dissociation expansions are presented. The emission intensity modulation evident in medium resolution fluorescence excitation spectra was observed under jet conditions, and appears to be related to homogeneous interactions of EO+ with repulsive valence states.