On the Bethe approximation to the reactance matrix

The Bethe approximation to the reactance matrix is considered for electron-neutral-atom collisions. Analytic expressions are given for the matrix elements. For the special case of electron-neutral-atom scattering the sum rules of Burgess (1974) are simplified. Particular consideration is given to the problem of calculating cross sections for dipole transitions. Partial cross sections are presented for all non-exact resonance dipole transitions between hydrogen atom states, with n, n' or=11, 31, 51, 71, 91.