Core Relaxation and Interchannel Coupling Effects on the Ar 3s Photoionization Time Delay in the Vicinity of the 2p ThresholdsNew Submission

Wigner time delay [1] in Ar 3s photoionization has been investigated in the vicinity of the inner-shell 2p thresholds (~250 eV) using the relativistic-random-phase approximation with and without core relaxation (RRPA-R and RRPA, respectively). Our calculations include quadrupole transitions, which become dominant at emission angles near 90° owing to angular momentum geometry. Distinctive qualitative and quantitative features in the Ar 3s time delay in the vicinity of the 2p thresholds, owing to interchannel coupling between the 3s and 2p photoionization channels, are seen. While the RRPA and RRPA-R results agree well away from the 2p thresholds, they diverge significantly immediately above the 2p₁_/₂ threshold (up to ~20 eV above) , and the details of the differences are strongly dependent upon angle, e.g., at θ = 90°, RRPA predicts positive time delay while RRPA-R yields negative values near the 2p₁_/₂ threshold. This study extends prior work on the Ar 3s Cooper minimum [2] to the unexplored 2p threshold region, representing the first investigation into the combined effects of core relaxation and quadrupole transitions. [1] R. Pazourek et al, Rev. Mod. Phys. 87, 765 (2016); [2] R. Khademhosseini et al, Phys. Rev. A 108, 063107 (2023).