Electron swarm characteristic energies (Dr/μ) in methane, perdeuteromethane, silane, perdeuterosilane, phosphine and hydrogen sulphide at low E/N

Measurements of the ratio of lateral diffusion coefficient to mobility (D r / mu ) have been made at 293 K for electron swarms moving under the influence of a uniform electric field in pure methane, perdeuterated methane, silane, perdeuterated silane, phosphine and hydrogen sulphide at low values of E/N (ratio of applied electric field to gas number density) where the only possible inelastic processes are rotational and vibrational excitation. For the methanes and silanes, the measurements extend over a wider E/N range than previous ones; there is good agreement with former results over the E/N ranges of overlap. The present D r / mu values are the only ones available for phosphine and hydrogen sulphide.