Resonant photoionization of singly charged sulfur

Abstract

Resonance structures in the photoionization of S{sup +} for the removal of a 3p or 3s electron from the ground 3s{sup 2}3p{sup 3} {sup 4}S{sup o} and excited metastable {sup 2}D{sup o} and {sup 2}P{sup o} states have been studied in the B-spline R-matrix approach. The nonorthogonal orbitals have been used for an accurate representation of the initial S{sup +} bound states, the final S{sup 2+} ion plus photoelectron states and S{sup 2+} thresholds. Calculations have been carried out in 17- and 27-state close-coupling approximations. The relativistic effects have been incorporated in the Breit-Pauli Hamiltonian. Photoionization cross sections are dominated by 3s{sup 2}3p{sup 2}({sup 1}D)ns {sup 2}D, 3s{sup 2}3p{sup 2}({sup 1}D)nd {sup 2}F, {sup 2}D, {sup 2}P, and 3s3p{sup 3}({sup 5}S{sup o}, {sup 3}S{sup o}, {sup 3}D{sup o}, {sup 3}P{sup o})np {sup 4}P Rydberg series of autoionizing resonances. The resonance states are identified and analyzed to obtain resonance positions E{sub r}, effective quantum numbers n{sup *}, and widths {gamma}{sub r} using a procedure of eigenphase gradients. The resonance line shape and correlation parameters have also been determined. Photoionization cross sections have been calculated in both length and velocity formulations that exhibit very good agreement (within 5%) with each other formore » most photon energies. Our results are compared with a recent merged ion-photon beam experiment. Significant discrepancies between the theoretically predicted and experimentally measured resonance structures and continuum cross sections are noted.« less