Double photoionization of Be and Mg atoms using the R-matrix-with-pseudostates method

The R-matrix-with-pseudostates (RMPS) method is used to obtain total cross sections for double photoionization of Be and Mg atoms from their ground singlet and metastable triplet terms. Time-dependent close-coupling (TDCC) calculations are also carried out for the total and energy differential double photoionization cross sections of Mg from its ground term. The RMPS total ground-term cross sections for Be and Mg are in good agreement with results from TDCC and convergent close-coupling calculations at lower energies but are above them at higher energies. They are also in good agreement with the results of synchrotron measurements. The total cross sections for double photoionization from the triplet metastable terms of Be and Mg are found to be two to three times smaller than those from their singlet ground terms.