Vibrational relaxation of HBr (v″= 1) at 300 K

Abstract

The vibrational relaxation of HBr(v″= 1) has been studied by flash photolysis with kinetic absorption spectroscopy in the vacuum ultra-violet. Two photochemical systems have yielded this vibrationally excited species. On photolysing hydrogen bromide, HBr(v″= 1) arises from the energy transfer process, Br(4²P_½)+HBr(v″= 0)→Br(4²P)+HBr(v″= 1). In the presence of added molecular bromine, the fast metathetical reaction H(1²S_½)+Br₂→HBr(v″=n)+Br(4²P_½,) takes place and is followed by rapid vibrational exchange to yield a non-Boltzmann population in the first vibrational level. This latter process was a convenient source for energy transfer studies of HBr(v″= 1) and the probabilities for relaxation on collision with the species He, Ar, H₂, HBr, HCl, N₂, CO, CH₄, SF₆, Br₂ and Br(4²P) are reported for 300 K. These data are discussed within the context of existing theories for vibrational relaxation.