Relativistic and correlation effects in np photoionization Cooper minimum of high-Z atoms

When the initial bound state radial function involved in the photoionizing transition has a node, the photoionization often passes through a zero, or near-zero, that leaves imprints on photoionization parameters like cross section, angular distribution asymmetry parameter, phase shift and time delay. This minimum is well-known as the Cooper minimum (CM) [1,2] which is quite sensitive to relativistic and correlation effects. Earlier, the CM for the 6p subshell were studied for high-Z atoms up to Z=100 using uncorrelated nonrelativistic Dirac-Slater central-field wave functions [3,4]. The present work extends these studies up to Z=120, using the correlated relativistic random phase approximation (RRPA) [5] and the Dirac-Fock independent particle approximation [6] for comparison; photoionization also from the 5p and 4p shells has also been examined. In particular, the atoms Rn (Z=86), Ra (Z=88), No (Z=102), Cn(Z=112), Og (Z=118), Ubn (Z=120) are investigated. Spin-orbit and interchannel coupling effects are of crucial importance to location of the CM at high Z. [1] J. W. Cooper, Phys. Rev. A, 128, 681 (1962). [2] W. R. Johnson and K. T. Cheng, Phys. Rev. A 20, 978 (1979). [3] S. T. Manson, et al, Phys. Rev. A 28 (1983). [4] P. C. Deshmukh, B. R. Tambe and S. T. Manson, Austral. J. Phys. 39, 679 (1986). [6] M. Reiher and A. Wolf, Relativistic Quantum Chemistry: The Fundamental Theory of Molecular Science, 2nd Edition (Wiley-VCH, Wertheim, Germany, 2015). [5] W.R. Johnson and C.D. Lin, Phys. Rev. A 20, 964 (1979).