Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization   Cross Sections of Atoms and Ions
  We present a complete set of analytic fits to the non-relativistic photoionization cross sections for the ground states of atoms and ions of elements from H through Si, and S, Ar, Ca, and Fe. Near the ionization thresholds, the fits are based on the Opacity Project theoretical cross sections interpolated and smoothed over resonances. At higher energies, the fits reproduce calculated Hartree-Dirac-Slater photoionization cross sections. 
D. A. Verner, G. J. Ferland, K. T. Korista (University of Kentucky),   D. G. Yakovlev (Ioffe Institute)