Photoionization cross sections for the helium isoelectronic series

The cross sections for photoionization of He, Li + , B 3+ , O 6+ , Ne 8+ and Mg 10+ are calculated in both the length and velocity formulations using the Hartree-Fock wavefunction for the continuum state and a 20 parameter correlated wavefunction for the ground state. Relativistic effects are not considered. The results are estimated to be accurate to about 1%. It is also shown that the calculated cross sections may be used to derive accurate photoionization cross sections for other ions in the helium isoelectronic sequence and specific results are given for Li + , Be 2+ , B 3+ , C 4+ , N 5+ , O 6+ , F 7+ , Ne 8+ and Mg 10+ . The theoretical values for two electron ions are found to be in good agreement with measured K shell photoionization cross sections.