Valence and L-shell photoionization of Cl-like argon using R-matrix techniques.

Photoionization cross-sections are obtained using the relativistic Dirac Atomic R-matrix Codes (DARC) for all valence and L-shell energy ranges between 27 and 270 eV. A total of 557 levels arising from the dominant configurations 3s²3p4, 3s3p5, 3p6, 3s²3p³[3d, 4s, 4p], 3p53d, 3s²3p²3d², 3s3p43d, 3s³p³3d² and 2s²2p53s²3p5 have been included in the targetwavefunction representation of the Ar III ion, including up to 4p in the orbital basis. We also performed a smaller Breit-Pauli (BP) calculation containing the lowest 124 levels. Direct comparisons are made with previous theoretical and experimental work for both valence shell and L-shell photoionization. Excellent agreement was found for transitions involving the ²Po initial state to all allowed final states for both calculations across a range of photon energies. A number of resonant states have been identified to help analyse and explain the nature of the spectra at photon energies between 250 and 270 eV. [ABSTRACT FROM AUTHOR]