Abstract
The discrepancy between previous R-matrix calculations using fixed boundary conditions and the eigenchannel method for the photoionization spectrum of barium is resolved. In particular, it is shown that the position of the (6p2)1S0 resonance that results in a maximum of the experimental photoionization cross section near 44800 cm-1 relative to the (6s2)1S0 ground state of barium cannot be obtained by a standard close-coupling expansion involving only physical bound states; instead, the correct representation of short-range correlation effects and the relaxation of the 6p orbital requires the inclusion of doubly excited configurations of the continuum-continuum type.

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