PHOTOIONIZATION OF HE-LIKE SYSTEMS BELOW THE N = 2 THRESHOLD

We have implemented a recently proposed L2-integrable basis method to study photoionization of He-like systems below the n = 2 threshold in the framework of a Fano-Feshbach theory. Non-resonant background cross sections and Fano parameters for the (2,n)1P(o) doubly excited states of He and Li+ up to n = 5 are calculated. For n greater-than-or-equal-to 3, an anomalous behaviour of the profile parameter q is found in He, which is the result of the existence of interfering, but nevertheless non-overlapping, resonances in the (2,nb) and (2,nc) series. The behaviour of photoionization parameters as a function of the nuclear charge is also discussed.