Probability of Ionization of Gas Molecules by Electron Impacts. II Critique

Abstract

Corrections to results of Hughes and Klein. Three sources of error are found and approximate corrections for them determined. They are (1) an effect of the electric field on the effective area of holes in the grid through which the primary electrons pass, which introduces corrections varying from -18 percent at the lowest voltages to +14 percent at 300 volts; (2)presence of slow secondary electrons and lack of uniform velocity of electrons in the primary electron stream, which necessitate additive corrections ranging from 30 to 50 percent; (3) warming of the gas by the filament, necessitating an additive correction of 12 percent. Correction to our previous results. Owing to lack of uniformity of velocities of electrons in the primary electron stream, we must add corrections of 24 percent at 45 volts, 11 percent at 100 volts and 9 percent beyond 125 volts. With these corrections the results from these two sets of experiments are in fair agreement. Curves show the final values for the probability that an ionizing collision will be made in a cm path in the gas at 0.01 mm pressure and 25°C by an electron of any speed up to 400 volts in He, Ne, A, ${\mathrm{H}}_2$, ${\mathrm{N}}_2$, Hg, HCl, and also for the probabilities of ionization at an impact in these gases.