Penning and dissociative ionizations of methane molecules in collisions with metastable helium atoms

Measurements of relative ion production yields in the Penning and dissociative ionizations of methane molecules on impact of metastable helium atoms have been carried out using a new crossed-beam apparatus, ''Perfectron''. Due to the perfect focusing property of the perfectron, the total ion yield as well as differential ion yield of each reaction channel can be measured. Though the measurement is at present only preliminary and no attempt is made to discriminate between 21S and 23S states in the primary helium beam, obtained spectra are in good agreement with those of Cermak et. al. and of Herce et. al. in the measurement of total ion yields. The CH3+ ions are most abundant in contrast with electron impact where the parent CH4+ ions predominate. On the other hand, in the measurement of differential ion yields at 00 with respect to the methane beam, the parent CH4+ ions slightly predominate over the fragment CH3+ ions. (author)