O IV: bound states, oscillator strengths and photoionisation cross sections

Close-coupling calculations were performed to obtain wavefunctions for the O 4+ +e scattering problem with incident energies between -5.667 and +0.95 Ryd. This energy range covers bound states and quasi-bound states of the O 3+ ion from 2s 2 2p 2 P 0 to 2p 2 ( 3 P)4d 2 D. The six terms arising from configurations 2s 2 , 2s2p, and 2p 2 of the target O 4+ were included in the calculation. The authors predict a number of high members of Rydberg series and doubly excited states hitherto not observed. Oscillator strengths for optically allowed transitions are given between most terms calculated and photoionisation cross sections for fifteen terms of O 3+ . The background behaviour of parentage allowed photoionisation cross sections can be simply calculated using a formula and program developed by Peach. It is shown that high bound states 2s 2 nl can contribute significantly to the population of states of the excited configuration 2s2p.