The parametrization of non-dipole processes in s-shell photoionization: spin-orbit interaction effects

The effect of the spin-orbit interaction on non-dipole processes in atomic photoionization from s-shells is examined. New formulae are derived for the parameters γ and δ that describe the forward-backward asymmetry of the photoelectron angular distribution. It is found that δ may be non-zero, unlike in the non-relativistic central-field model. The reactions ns → εl and ns2 → nsεl are considered separately and it is shown that the latter case may be economically given in terms of singlet and triplet continuum state amplitudes. The spin-orbit interaction in intermediate autoionizing states introduces a strong energy dependence into the non-dipole parameters and this may be used to determine relative phases of the continua. It is suggested that Xe 4d-1nl odd and even parity autoionizing levels are a possible system for experimental investigation