Resonant structures of overlapping doubly excited autoionization series in photoionization of Mg-like Al⁺sand Si²⁺sions

We present a quantitative study of the resonant structures of the overlapping 3pνd ¹F and 3pνg ¹F autoionization series in the photoionization from the bound excited ¹D states of Mg-like Al⁺ and Si²⁺ ions. The interference, both constructive and destructive, between the contributions from individual processes corresponding to transitions from specific initial to final-state configurations, are examined in detail. Our calculation shows that the photoionization from higher bound excited 3sν_id ¹D state is dominated by the shakeup of the outer d electron following the 3s→3p core electron excitation. For Al⁺ , our calculation reveals the presence of a narrow 3pνg ¹F window resonance located on the higher-energy shoulder of its corresponding broad 3pνd ¹F resonance. Unlike the usual isolated window resonance, which is dominated by the transition from the initial state to the continuum component of the final-state wave function, the 3sν_id ¹D→3pνg ¹F window resonance results primarily from the energy variation of the bound component, i.e., the weighted νd radial function, of the final-state wave function in the vicinity of the 3pνg ¹F resonance.