Neutral dissociation of methane by electron impact and a complete and consistent cross section set

We present cross sections for the neutral dissociation of methane. With these cross sections the work of Song et al. [J. Phys. Chem. Ref. Data, 44, 023101, (2015)] can be extended which results in a complete and consistent set. Notably, the resulting cross section set does not require any swarm-fitting to reproduce swarm parameters. Therefore consistency can be considered an inherent trait of the set, since swarm calculations (with a Monte-Carlo code) are used exclusively for validation of the cross sections. Neutral dissociation of methane is essential to include (1) because it is a crucial electron energy sink in methane plasma, and (2) because it largely contributes to the production of hydrogen radicals. Finally, we compare the production rates of hydrogen species for a swarm-fitted data set with ours. The two consistent cross section sets predict different production rates, with differences of 45% (at 100 Td) and 125% (at 50 Td) for the production of H₂ and a similar trend for production of H. With this comparison we underline that the swarm-fitting procedure can possibly deteriorate the accuracy with which chemical production rates are estimated. This is of particular importance for applications with an emphasis on plasma-chemical activation of the gas.