Multichannel Photo-Ionization of Atomic Systems

Abstract

Expressions for multichannel photo-ionization are obtained with the dipole approximation assuming $\mathrm{LS}$ coupling; while including the effects of coupling between channels, these expressions give separate contributions for each channel. The explicit form of the cross sections for atomic systems with configurations $1s^{2}2s^{2}2p^q$ is obtained, assuming superpositions of determinantal wave functions (Hartree-Fock) for initial and final states. The effects of core relaxation are considered. The formalism is applied to the photo-ionization of neon, with the result that coupling between channels and core relaxation have a larger effect on the individual channel cross sections than on the total cross section. Both effects tend to bring the dipole velocity and length forms of the cross section into closer agreement with each other, but the improvement is appreciable only near threshold.