Reactions of Recoil Bromine Formed by the ^76,77Kr→^76,77Br Systems with Simple Hydrocarbons. Pressure and Additive Effects on Gas-Phase Reactivity

Recoil bromine species produced by the systems ^76,77Kr →^76,77Br were reacted with a series of hydrocarbons in the gas phase over the density range 2 X 10^-5 to 0.5 g/cm³. In the region below 100 atm differences in reactivity are related to differences in decay modes and recoil energies. In the low-density methane system an ion-molecule mechanism involving excited CH4Br+ is suggested. At higher pressures, the yields are explained in terms of the onset of “caging” reactions due to autoradiation effects. At high percent “inert” moderator, yields increased for CH₄, above those of the pure methane system. Brominating complexes such as KrBr⁺ and ArBr⁺ are hypothesized to explain the results.