The dynamics of electronically excited states in the rare-gas–halogen systems
Abstract
Detailed studies of the reactions of electronically excited IBr[E(0+)] with Xe, translationally excited Xe(3P2) with I2, Br2 and ICl, and Kr(3P2) with Br2 are reported.
Vibrationally excited levels in the E(0+) ion-pair state of IBr were pumped using tunable synchrotron radiation and the ‘vibrational’ excitation function for XeBr(B) formation determined for energies ⩽66 kJ mol–1 above threshold. Branching ratios for XeBr(B)vs. XeI(B) formation, together with data for the alternative excitation-transfer channel have also been determined over the same energy range.
Fully dispersed chemiluminescence spectra and their polarizations have been measured under superthermal atomic beam [Xe(3P2), Kr(3P2)]–Maxwellian gas (I2, Br2, ICl) conditions at average collision energies Ēcm < 120 kJ mol–1. These have revealed distinctive patterns of behaviour for the collisional energy dependence of branching into alternative atom- and excitation-transfer channels and of vibrational energy and rotational angular momentum disposals.
A simple global model is presented to reconcile the varying patterns of behaviour found in the rare-gas–halogen systems under both ‘collisional’ and ‘complexed’ conditions, and in particular the dependence on the initial reagent state preparation.