Multiple Scattering of Electrons. II

The series developed in a previous paper representing the distribution for the multiple scattering of electrons has been evaluated numerically for a large number of cases; the results are given in Table I. An approximate expression is found for the value of sin θ averaged over the distribution per unit solid angle, f(θ). This expression, which agrees within a few percent with the exact computation, is w〈sin θ〉Av~1.76A1/2(5.60-1/3 log Z+1/2 log A)1/2, in which w is the energy in units mc² and A=24.8×10^-26Z²Nt. For the scattering intensity per unit solid angle at 0^∘{}, that is $f(0)$, an approximate relation is 4πf(0)w²~0.43A(5.60-1/3 log Z+1/2 log A). The accurate calculations show also that f(θ)w² is almost independent of the energy. A series formula is derived for the projected scattering distribution as observed in a cloud chamber. The averages of w sin α, α being the projected angle, are given in Table VI. These averages are smaller than the values computed by Williams and show a variation with energy. It is believed that the largest inaccuracy remaining in the results given is due to uncertainties in the single scattering law.