Calculation of the energy per ion pair forα-particles in helium

Abstract

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