Low Energy Photoionization in the Ar Isoelectronic Sequence: Complex Effects of Z
Valence 3p photoionization of neutral Ar and several ions isoelectronic to it is investigated in the low photon-energy regime using the relativistic-random-phase approximation. With increasing Z, a steady shift of “Cooper minimum” towards the ionization threshold is seen in the cross section such that at sufficiently high Z it crosses the threshold to enter the discrete of 3p channel. Further, a remarkable threshold feature is observed for some ions that essentially originates from strong Z-dependent interaction with inner 3s photoexcitation series. Results strengthen our previous caution against any indiscriminate interpolation (or extrapolation) of ionic data at low energies.
KeywordsIonization Threshold Isoelectronic Sequence Cooper Minimum Atomic Photoionization Steady Shift
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