Reaction cross sections and threshold energy in the reaction of isotopically pure H atoms and ethane

Abstract

Reaction cross sections and threshold energy have been determined for the first time for the isotopically pure reaction, H+C2H6→H2+C2H5. Taking measured reaction probabilities from photochemical studies of the isotopically pure reaction and from xenon moderated systems, calculations described here of H atom collision densities in Xe by a stochastic method allowed the evaluation of reaction cross sections. These rise from the threshold energy at 43±2 kJ mol−1 to a maximum value of ∼8×10−3 nm2 in the vicinity of 100 kJ mol−1. The excitation function in this energy range is close to a line-of-centers function. The cross section values per C–H bond are higher than for the isotopically mixed H+C2D6 reaction, similar to the primary C–H bonds in C3H8, but lower than for secondary C–H bonds in C3H8. All these values are small compared with the total collisional cross section.