Mechanism of Electron Capture and Hydrogen Formation by HBr Irradiated in Mixtures with C2F6, CO2, and Xe

The gas phase 60Co γ-radiolysis of HBr in mixtures with C2F6 and CO2 has been studied at room temperature, using doserates determined from ionization chamber measurements. A new value of [Formula: see text] is reported, but [Formula: see text] was in agreement with earlier work. Ionization yields and hydrogen yields in the mixtures followed a linear energy partitioning equation.The increase in the fraction of scavengable electrons with increasing pressure of buffer gas can be satisfactorily explained by enhanced moderation of the energies of subexcitation electrons. A study of the competition for thermal electrons between SF6 and HBr indicates that the rate of electron capture by HBr maintains a second order dependence on HBr pressure over the 50 to 600 Torr range both in the presence and absence of buffer gas. There was no evidence for the collisional stabilization of HBr−* by the buffer gases and it is pointed out that thermal electron capture may involve (HBr)2 dimers.