The photoionisation of the O+(4So) ground state

The photoionisation of the O + (2s 2 2p 3 4 S o ) ground state is studied starting from an accurate physical model. The initial bound state O + ( 4 S o ) and the final continuum state (O 2+ +e - ) ( 4 P e ) are described consistently by collisional R-matrix-type expansions over six parent ionic states: O 2+ (2s 2 2p 2 3 P e ; 2s2p 3 5 S o , 3 D o , 3 P o , 3 S o ; 2p 4 3 P e ), represented by accurate configuration interaction wavefunctions. Detailed graphs and tables provide information on the total and partial cross sections, the angular distribution of photoelectrons and the analysis of prominent resonant structures. Some of the present results are compared with previous work concerning the photoionisation of neutral nitrogen.