Abstract
Cross sections for s, p and d have been computed in the framework of a single-electron model (non-relativistic) by using a parametric central potential. The evolution of the non-hydrogenic behaviour of photoionization cross sections near threshold is studied along Rydberg series; non-hydrogenic characters are particularly large for all the ns series and for the np series of K. The validity of the method is discussed and it appears that sigma sigma np and sigma nd values are more reliable than sigma ns. The results are compared to experimental data and other theoretical results, mainly provided by the quantum-defect theory. The agreement between the various results is generally very good for sigma np and sigma nd; the agreement is satisfactory even for the most unfavourable cases provided by sigma ns of Na and K.