Comparison of the acceleration, length, and velocity forms of the dipole operator in photoionization calculations

Abstract

The acceleration, length, and velocity forms of the dipole operator are used to calculate the subshell photoionization cross sections in argon. First-order electron correlation corrections to the Hartree-Fock approximation are obtained through the use of many-body perturbation theory. For low-energy transitions the acceleration form of the operator is found to give very large errors in the Hartree-Fock approximation as compared to the length and velocity operators. Correlation effects for the three operator formulations are found to be quite different.