Photoionization Branching Ratios of Spin-Orbit Doublets in Rn Far Above Thresholds

At energies far above the branching ratios of the photoionization cross section of spin-orbit (nl) doublets must go to its statistical value of (l+1)/l in the absence of relativistic effects. Thus, alteration of the branching ratio from its statistical value at higher energies indicates relativistic interactions on the initial and final state radial wave functions as predicted earlier [1] and verified experimentally recently [2]. Here we report on a study of Rn (Z=86) using the relativistic-random-phase approximation (RRPA) based on the Dirac equation, which includes relativistic interactions in an ab initio manner and many-body correlations. The results show that branching ratios well above the threshold are not only energy-dependent and move further away from the nonrelativistic value with increasing energy, but also that interchannel coupling effects in the vicinity of inner-shell thresholds, as suggested by earlier studies [3,4]. Particularly strong interchannel effects are seen near the 3d thresholds. . [1] A. Ron, Y. S. Kim, R. H. Pratt, Phys. Rev. A 24, 1260 (1981); [2] R. Puettner, et al, J. Phys. B 54, 085001 (2021). [3] E. W. B. Dias, et al, Phys. Rev. Lett. 78, 4553 (1997); [4] W. Drube, et al, J. Phys. B 46, 245006 (2013).