PHOTOIONIZATION FROM 1SNS (1,3)S(E) STATES OF HELIUM

We present theoretical photoionization cross sections from the 1sns 1, 3S(e) bound excited states of the helium atom based on a configuration -interaction procedure for the continuum, using a finite L2-basis set constructed from a nearly complete set of B-spline-based one-particle hydrogenic orbitals. In addition to the nonresonant spectra near the f irst ionization threshold, resonant structures associated with selecte d sp,2n+/- and 2pnd 1,3P(o) autoionization series below the He+ N = 2 threshold are examined in detail. The widths and resonance energies of all 1,3P autoionization series are also reported and compared with ot her available theoretical and experimental results.