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The angular asymmetry parameter β fl of the photon-induced fluorescence radiation of Ar + (4p-4s) fine-structure resolved satellite lines was measured from threshold up to 38.4 eV. It is well known that the cross sections of these valence shell satellites are dominated by the decay of aligned doubly excited states leading to an extremely complicated energy dependence. In contrast, we observe that the β fl parameter becomes less structured with increasing total angular momentum J of the photoion. The β fl measurements can be interpreted by a partialwave analysis of the photofragmentation products. For the population of the 4p 2 F 7/2 ion state only d 5/2 photoelectrons are emitted on all resonances. For the population of the 4p 2 D 5/2 and the 4p 4 P 5/2 ion states the emission of the parity-unfavoured d 5/2 photoelectrons dominates.

The absolute cross sections for the 3s-photoionization and the 3p-photoionization of the Ar atom and the Ar-like ions K+ and Ca2+ are calculated. The calculation is performed within the configuration-interaction technique using the Pauli-Fock atomic orbitals. The simultaneous analysis of the calculated and measured total and partial cross sections yields the interpretation of the prominent resonances observed in a recent experiment on Ar above the 3s-threshold.

The lifetimes of the ns1 np6 2S1/2 states of Ar II, Kr II and Xe II were determined by measuring the fluorescence decay curves after selective excitation with pulsed monochromatized synchrotron radiation. The lifetimes are Ar = (4.684±0.019) ns, Kr = (30.78±0.17) ns, and Xe = (35.93±0.20) ns. Calculations performed within the configuration interaction approach show the strong dependence of the calculated lifetimes on the configuration interaction. It is proposed to use the precise lifetime values for a test of future calculations of the effective value of the Coulomb interaction of electrons.