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K and L x-ray transition probabilities have been calculated for several elements between Z=92 and 170. The calculations include multipoles higher than $E1$, are relativistic, and utilize Dirac-Hartree-Fock wave functions with finite-size nuclei. At these very high atomic numbers many transition rates go through a maximum as a function of Z, and other transitions show a maximum and a minimum, and then begin to increase again past $Z=150$.
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Anholt et al. (1974) studied this question.
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