Photoionization of two-electron atoms using a nonvariational configuration-interaction approach with discretized finite basis.

We present an extension of a simple configuration-interaction procedure to the photoionization of two-electron atoms. By using a finite basis set constructed from {ital B} splines, this nonvariational approach does not rely on any optimum procedure, which is often required in other more elaborate configuration-interaction calculations. The quantitative accuracy of this procedure is tested by examining the photoionization cross sections at photon energies immediately above the first ionization threshold, as well as near the doubly excited 2{ital s}2{ital p} {sup 1}{ital P} resonance structure. The {ital S}- and {ital P}-wave phase shifts for the electron-hydrogen scattering calculated with this procedure are also presented. The excellent agreement between the present calculation and other existing theoretical and experimental results, in addition to the extensive recent applications of this procedure to the bound excited states of divalent atoms, has further demonstrated the effectiveness of this simple configuration-interaction procedure.