Merging of positions of zeros in dipole and quadrupole matrix elements of photoeffect from outer-shell and Rydberg states of high- Z elements

The zeros in dipole and quadrupole matrix elements of photoeffect from the ns1/2 subshells of uranium approach common positions as n→∞. This is an illustration of the more general feature that for sufficiently large n₀ photoeffect cross sections and angular distributions from nJL subshells, aside from the bound-state normalization factor which scales the cross section, are the same for all n>n₀ (J, L fixed) except for energies very close to threshold. This behavior can be expected for all subshells and all elements and for all multipole matrix elements.