Energy losses of electrons in nitrogen

Abstract

Critical potential measurements in nitrogen have been published by several investigators. In most of this work the excitation and ionisation potentials were located by the sudden changes in the current to a detecting electrode, produced by photoelectrically active radiation or by positive ions as the accelerating voltage was raised above the critical value. Recently a good deal of information has been secured by the application of positive ray analysis and by combined electric and spectroscopic observations. In an extensive study of the scattering of electrons and ions in gases at rather high pressures Langmuir and Jones have measured energy losses of electrons by a kind of retarding potential method. Harnwell studied the angular distribution of scattered electrons in a number of gases; by means of a radial, inverse first power, electrostatic field, in which the electrons were deflected through 90°, he was able to measure the velocity of the electrons after scattering. He found a broad maximum in the distribution curves for nitrogen, indicating inelastic collisions with a most probable energy loss of some 12⋅9 volts. No other direct measurements of the energy losses in single collisions in nitrogen appear to have been made. The present investigation is an attempt to measure with a higher accuracy the energy given up by electrons at inelastic impacts in nitrogen under such conditions that no appreciable amount of multiple collisions should occur. Only collisions for which the resulting deflection of the colliding electron from the original line of flight is very small can be studied with the apparatus used.