Energetic H atoms from the photolysis of HBr and HI. Threshold energy and cross-section for the D abstraction reaction between H and CH3CD2CH3

Abstract

The reaction of photochemically generated “hot” hydrogen atoms with CH₃CD₂CH₃ has been examined and the integral reaction probability of the abstraction reaction (1) determined at different translational energies of H^*: H^*+ CH₃CD₂CH₃→ HD + CH₃CDCH₃. (1), The phenomenological threshold (laboratory energy) of reaction (1) is 40 ± 4 kJ mol^–1. The moderating effects of xenon and carbon dioxide have been measured, and it is found that moderation of H^* by CH₃CD₂CH₃ becomes more effective relative to moderation by Xe as the energy is increased. The cross-section for reaction (1) has been obtained from measurements of the moderating effect of Xe by using calculated collision densities of H in Xe. The average cross-section over the approximate range 66–197 kJ mol^–1, normalised to a single D atom, is (1.5 ± 0.4)× 10^–3 nm².