Simplified version of the random-phase-approximation-with-exchange method

By comparing the random-phase-approximation-with-exchange (RPAE) method of Amusia et al. for the calcuation of photoionization cross sections from closed-shell atoms with the reaction-matrix method, we obtain a simplified version of the RPAE by which we calculate the dipole-transition amplitude much as in the reaction-matrix method, yet with ground-state correlation effects included simultaneously. Calculation of photoionization cross sections for the 3p→εd transition of Ar and 4d→εf transition of Xe by this method yields a substantial improvement on the calculation by the reaction-matrix method and good agreement with RPAE and with experiment.