Relaxation and non-RPA Effects in Photoionization Time Delay of Ar 3s and 3p subshells

Photoionization studies of the inner and outer subshells of atomic argon have been extensively reported in literature [1-6]. Photoionization cross sections, angular distribution asymmetry parameter, branching ratios, phase of the matrix elements and the photoionization Wigner time delay for argon have been reported at using different computational techniques [1-6]. Alexandridi et al., [6] have reported the experimental results of atomic delay difference between the 3s and 3p subshells of argon in the region of 3s (38 eV – 45eV) and 3p (45eV to 60eV) Cooper Minimum (CM) photon energy. A discrepancy between the experimental data and the theoretical calculations using 2P2C RPAE technique [6] is observed to be more significant in the region of 3s CM when compared to the region of 3p CM. The present work aims to calculate the photoionization time delay in this energy range of argon in the presence of relaxation effects using RRPA- R approximation [7], and non-RPA correlations using the RMCTD [8-9] approximation. It is predicted that inclusion of important non-RPA correlations improves the agreement with experimental results and help understand the dynamics of argon photoionization. Ref: [1] D.J. Kennedy and S.T. Manson Phy. Rev. A, 5 (1972). [2] R.G. Houlgate et al., J.Phys. B, 7 (1974) [3] M. Kutzner et al., Phy. Rev. A, 55 (1997) [4] A. Kheifets et al., Phys. Rev. A 94, 2016 [5] S. Saha et al., Phys. Rev. A, 90 (2014) [6] C. Alexandridi et al., Phys. Rev. Research, 3 (2021) [7] V. Radojevic, et al., Phys. Rev. A 40 727-734 (1989) [8] V Radojevic and W. R. Johnson Phys. Rev. A 31, 2991 (1985). [9] Jose J et al., Phys. Rev. A83 053419 (2011).