IONIS: Approximate atomic photoionization intensities Original Research Article

A program to compute relative atomic photoionization cross sections is presented. The code applies the output of the multiconfiguration Dirac–Fock method for atoms in the single active electron scheme, by computing the overlap of the bound electron states in the initial and final states. The contribution from the single-particle ionization matrix elements is assumed to be the same for each final state. This method gives rather accurate relative ionization probabilities provided the single-electron ionization matrix elements do not depend strongly on energy in the region considered. The method is especially suited for open shell atoms where electronic correlation in the ionic states is large.