We present a combination of the R-matrix theory with time dependence (RMT) method with density matrix theory to model sequential ionization processes. Separate RMT calculations model the individual ionization stages, while a density matrix describes the coherences within the intermediate ion. As proof of concept, we quantify changes in the angular distribution of photoelectrons in the final stage of sequential ionization of Ne + to Ne 3 + by x-ray free-electron laser radiation with photon energies of 95 eV.
H. W. van der Hart (Mon,) studied this question.