Efficiency of Ionization in Hydrogen by Positive-Ion Impact At 7000 Volts

Abstract

Hydrogen at low pressure is bombarded with potassium positive ions of 7000 volts energy in a tube attached to a positive-ray box. Any hydrogen ions and scattered potassium ions passing into the latter are distinguished by mass analysis. The applicability of this method for measuring the efficiency of ionization is discussed. If the hydrogen molecules receive kinetic energy from the 7000-volt ions which ionize them, they will be scattered in all directions, and only those which happen to be projected towards the slit will enter the positive-ray box. But if ionization is unaccompanied by transfer of kinetic energy, the method is competent to compare the ionizing efficiency with that of electron-impact. With small positive-ion emissions no ionization was detected; with larger emissions a violent discharge took place through the tube. The conclusion reached is that either the ionizing efficiency is less than $\frac{1}{150}$ of that of 50-volt electrons, or else that ionization is accompanied by transfer of kinetic energy.