Photolysis quantum yields and atom recombination rates of bromine in compressed gases. Experiments up to 7 kbar

Photolysis quantum yields of Br2 and recombination rates of bromine atoms have been measured by nanosecond laser flash photolysis at 532 nm. The influence of the pressure of the bath gases He, Ne, Ar, and N2 was studied over the range 1–7000 bar. Measurements in CO2 were performed up to 60 bar, in C3F8 up to 8 bar. Diffusion control of the atom recombination, with decreasing recombination rates at increasing bath gas densities, could be established for Ar and N2. Photolytic cage effect, i.e., decreasing photolysis quantum yields with increasing densities, was observed for all gases. The results are expressed in terms of simple models applied earlier to similar phenomena in iodine photolysis. The combination of quantum yield and recombination data allows for separation and semiquantitative representation of two mechanisms for geminate recombination, i.e., stabilization in clusters and cage energy relaxation.