L1–L3 Coster–Kronig and Li (i = 1,2,3) sub‐shell fluorescence yields for Th and U

Abstract

AbstractThe L1–L3 Coster–Kronig yield, f13, for Th and U was determined using measured intensities of the Lα x‐rays emitted following selective ionization of the L3 sub‐shell by Mo K x‐rays (B < Einc. < B) and of those emitted following ionization of the Li (i = 1,2,3) sub‐shells by the 59.54 keV γ‐rays (B < Einc. < BK), where B is the K shell/Li sub‐shell ionization threshold of the target element. The measurements were performed using an energy‐dispersive x‐ray fluorescence set up involving an Si(Li) detector and photon sources consisting of an 241Am radioactive annular source used in (i) the direct excitation mode and (ii) the secondary excitation mode together with the Mo secondary exciter. In addition, the Li (i = 1,2,3) sub‐shell fluorescence yields (ωi) for Th and U were deduced using our earlier measured x‐ray fluorescence cross‐sections at incident photon energies in the range 17–60 keV and the theoretical photoionization cross‐sections. The measured f13 and ωi yields were compared with the available semi‐empirical values and the theoretical values based on relativistic Hartree–Dirac–Slater (RDHS) calculations. Copyright © 2002 John Wiley & Sons, Ltd.