The Drift Velocity of Electrons in Water Vapour at Low Values of E/N

Abstract

The drift velocity of electrons in water vapour at 294 K has been measured over the E/N range 1·4 to 40 Td with an error estimated to be <±O· 5% for 5 < E/N (Td) < 35 and ± 0·7% for E/N < 5 Td and E/N> 35 Td. The present data show that J.lN decreases monotonically with decreasing E/N at low E/N values as observed by Wilson et al. (1975) and does not become independent of E/N as indicated by Lowke and Rees (1963). The present values, although lower than those of Lowke and Rees, lie within the combined error limits, except for values below 2 Td. The present data suggest that the momentum transfer cross section at low energies is approximately 10% larger than that obtained by Pack et al. (1962) from their drift velocity measurements.