L1 Atomic-Level Widths Of Heavy Elements

High-resolution measurements of the L1-M4,5 fluorescence x-ray lines of Sm, Ho, Yb, W, Pt, Hg and Bi were performed, using a transmission DuMond-type and a reflection von Hamos-type bent crystal spectrometer. Despite the poor intensity of the dipole-forbidden transitions, precise linewidths were obtained. Assuming for the M4,5 level widths the values reported recently by Campbell and Papp, the L1 level widths of the investigated elements could be determined with a precision of 4-10%. A good agreement with Campbell and Papp's data was observed for the heaviest elements. For Sm and Ho, however, an intriguing discrepancy was found. The latter was explained by a splitting effect of the L1 subshell resulting from the coupling of the 2s electron spin in the initial excited state with the total spin of the open 4f level. Based on this splitting picture, adjustements of the L1 level widths recommended by Campbell and Papp were proposed for the lanthanides region.