Drift of positive ions of methane in parent gas

A drift tube-mass spectrometer was used to measured the mobility of CH5+, C2H5+ and C3H5+ in CH4 over a wide range of the reduced field strength, E/N, from 15 to 500 Td (1 Td = 10-17 V cm2). The zero-field mobilities of these ions turn out to be lower than those predicted by Langevin's polarization-limit theory. The low field mobilities for the first two ions are in good agreement with previous values obtained from other techniques. For E/N > 100 Td, the mobility of CH5+ is lower than that of C2H5+ sm-bullet suggesting a proton transfer process between CH5+ and CH4. The mobility curves show a pronounced maximum over the range 200-300 Td