XXIV. The capture and loss of electrons by α particles

Calculation of the energy per ion pair for α -particles in helium

The average energy per ion pair, W , for the ionization of helium by 1 to 6 MeV α -particles is calculated using the Born approximation, the number of ion pairs produced by secondary, tertiary, etc., electrons being calculated from an integral equation which is solved numeric­ally. The calculated W is nearly constant over this energy range, with average W = 41∙1 eV. This agrees well with the value, W = 42∙7 eV, measured recently by Jesse & Sadauskis for 5∙3 MeV α -particles in helium, and supports their suggestion that the earlier measured values of W for α -particles in helium may have been spuriously low owing to the presence of small amounts of other gases.