Ion–molecule reactions in the systems CF4–CH4 and CF4–C2H6

A mass spectrometric study of ionic reactions in CH4−CF4 and C2H6−CF4 mixtures was undertaken at pressures as high as 0.52 torr. It was found that CF3+ ions react in a hydride transfer process with ethane with a rate constant of 3.3×10−10 cm3 molecule−1⋅s−1. A rate constant of 1.6×10−10 cm3 molecule−1⋅s−1 was determined for the reaction of C2H5+ ions with C2H6. In mixtures of CH4 and CF4, both CH3+ and CH5+ react with CF4, apparently by fluoride ion transfer, for which we calculated rate constants of 8.6×10−10 and 2.3×10−10 cm3 molecule−1⋅s−1, respectively. CF3+ ions do not attack molecular methane. There is good agreement with published rate constants for the disappearance of CH2+, CH3+, and CH4+ ions in pure methane. However we observed a decreasing CH5+ yield above 0.1 torr which may be due either to impurities or to excess energy in CH5+ ions as a result of a relatively high repeller field strength within the ion source in our experiments.