Unusual behavior of Cooper minima of ns subshells in high-Z atoms

A study of Cooper minima (CM) arising from the photoionization of 6s, 5s, and 4s subshells of high-Z atoms has been performed using Dirac-Fock (DF), two-channel relativistic-random-phase approximation (RRPA), and fully coupled RRPA. The results show huge splittings between ns -> epsilon p(3/2) and ns -> epsilon p(1/2) CM which increase with Z owing primarily to the relativistic interactions (spin orbit) that are attractive for the epsilon p(1/2) final state but repulsive for the corresponding epsilon p(3/2). In addition, it was found that correlation in the form of interchannel coupling (essentially configuration interaction in the final continuum states) plays a huge role in determining the location of the CM. For 6s photoionization, the 6s -> epsilon p(3/2) and 6s -> epsilon p(1/2) CM behave completely different as a function of Z. It was also found that for 5s and 4s photoionization, the CM move below the threshold, with increasing Z, and, at high enough Z, the 5s -> epsilon p(3/2) and 4s -> epsilon p(3/2) CM re-emerge into the continuum. The calculations have been carried out for the ns subshells of Hg (Z = 80), Rn (Z = 86), Ra (Z = 88), No (Z = 102), Cn (Z = 112), and Og (Z = 118).