Abstract
Two-photon ionization processes from the ground state of strontium are studied employing the jj-coupled eigenchannel R-matrix approach combined with the multichannel quantum-defect theory (MQDT). The calculations satisfactorily reproduce the experimental spectra corresponding to two-photon excitation of the 4d6d J = O-e, J = 2(e) and 5p(2 1)S(0), D-1(2) low-lying autoionizing resonances, confirming that the method is suitable to account for the spin-orbit interaction effects in the multiphoton excitation of heavy atoms. it is also shown that the dielectronic core polarization cannot be disregarded in the description of these highly correlated resonances, as it affects significantly both their energy positions and autoionization widths.