Comparison between anion and cation emission from CH4 molecules colliding with 10.5-keV C+ ions: Fragment-energy aspects

It is shown that both positive and negative ions can be ejected from gas-phase methane molecules when bombarded with positive ions at keV energies. The kinetic energy distribution of the negatively charged fragments shows strong similarities with that of the ejected cations. However, in a hard binary collision between the C+ projectile and an H atom, the formation of H− ions is more endothermic than the formation of H+ ions.