Reactions of isomeric transition-activated 80Br in the Hsup(80m)Br-CH4 system

The reaction of isomeric transition-activated 80Br was studied in the gaseous Hsup(80m)Br-CH4(HBr/CH4=0.1+-0.01) system. CH380Br, CH280BrBr and CH80BrBr2 were identified as the products, and their absolute yields were 1.60, 2.65, and 0.05%, respectively. The effects of Kr and Xe additives show that these products were produced only through kinetic-energy independent (thermal ionic) processes. The results are compared with those obtained in the sup(80m)BrBr(or sup(82m)BrBr)-CH4 system, in which the C-*Br formation proceeds mainly via kinetic-energy dependent processes, and the difference between them is explained on the basis of the cross sections for charge neutralization and capture collision complex formation of bromine ions as a function of the kinetic energies initially acquired by the 80Br and 82Br atoms. The persistent complex ions, CH480Br+, is considered to be a precursor of the product formations, and the formation of individual products is discussed on the basis of ion-molecule reactions of CH480Br+ with surrounding molecules. Furthermore, the effect of HCl and CH2=CH2 additives on the yield distribution were examined to elucidate the reaction mechanisms of the product formations. (auth.)