Zero-field Mobility for Electrons in Dry and Humid Air

Abstract

The zero-field mobility of electrons in dry and humid air at 294 K has been studied with drift tube techniques. For air containing 1.5 % water vapour (50 % relative humidity) the zero-field mobility was found to be 8.4 ± 0.2 X 10⁵ cm s^−l Td^−l. The zero-field mobility of electrons in dry air (4.7 ± 0.2 x 10⁶ cm s^−l Td^−l) was deduced from measurements in which small quantities of CO₂ Were added to reduce the electron energy. It is estimated that the momentum transfer cross section for electron–oxygen collisions, at near thermal energies, is at least four times smaller than it is for electron–nitrogen collisions.