Vibrational relaxation of XeBr(B) by Ar

XeBr chemiluminescence spectra excited in the reaction of Xe(³P₂) with recorded in a flowing afterglow apparatus using Ar buffer gas at pressures in the range 0.5-5 torr. Vibrational distributions in the B(1/2) states were derived from the spectra by an inversion technique (ref 1) and subsequently analyzed to determine effective rate constants for the relaxation of XeBr(B) by Ar as a function of v′. These are upper limits to real constants for vibrational relaxation and are found to increase monotonically, rising from 0.2 × 10-¹⁰ cm³ molecule^-1 s^-1 at v′ = 30 to 10 × 10-¹⁰ cm³ molecule^-1 s^-1 at v′ = 150. XeBr spectra excited in the reaction of Xe(³P₂) with CBr₄ (ref 2) were also analyzed for comparison, to yield analogous results for 25 < v′ < 110. The unrelaxed vibrational population distribution in the Xe*/Br₂ system differs significantly from that determined previously (ref 2).