The Drift Velocity of Electrons in Mercury Vapour at 573 K

The drift velocity of electrons in mercury vapour at 573 K has been measured using the Bradbury-Nielsen time-of-flight method at vapour number densities ranging from 3·40x 1017 to 1·83x1018 cm-3 and at E/Nvalues from 0·1 to 3·0 Td. The measured drift velocities increase linearly with mercury vapour number density, the magnitude of the dependence being a function of E/ N. This number density dependence has been attributed to the presence of mercury dimers and the drift velocity corresponding to dimer-free mercury vapour has been obtained by extrapolation. Sources-of error are examined and the present results are compared with those of previous workers.