Drift velocity of electrons and ions in dry and humid air and in water vapour

Abstract

The avalanche current resulting from the release of a short (30 nsec) pulse of photoelectrons (5 × 104) at the cathode of a uniform field gap (5 cm) is observed experimentally. By this technique the drift velocities of electrons (v-) and of positive ions (v+) are measured. In dry air in the range E/p = 50-100 v cm-1 torr-1 at temperature 20 °c, v- = 256 × 103 E/p + 5 × 106 and in water vapour in the range E/p = 55-85 v cm-1 torr-1 at 20 °c, v- = 255 × 103 E/p + 8.9 × 106, with units cm sec-1 and v cm-1 torr-1. The values of v- obtained for dry air fit the values calculated by Heylen and are higher than those measured with the magnetic-deflection method by Townsend and Tizard.