The Ratio DT/µ for Electrons in Water Vapour at 294 K

Abstract

The ratio DT /� for electrons in water vapour (294 K) has been measured by the TownsendHuxley method as a function of E/N (where E is the electric field strength and N the gas number density) at vapour pressures ranging from 0 �103 to 0�413 kPa. For E/N 30 Td were found to be strongly pressure dependent, the strength and sign of the dependence depending on E/N and the current ratio relation used. Since extrapolation to infinite pressure at each E/N value did not give the same value of DT/ u, it has not been possible to derive reliable DT/ J.l values for this higher E/N range. Possible causes of the observed pressure dependences are discussed. The present data are in good agreement with the values predicted by Ness and Robson for values of E/N ~ 24 Td.