Coster-Kronig factorf13ofY39measured with the synchrotron photoionization method

The intensity of the $L_3$-$M_4$,5${\mathrm{M}}_4$,5 Auger line of ${}_{39}{}^{}{}_{}{}^{}\mathrm{Y}$ excited by photons with energies in the range of the $L_1$ edge has been measured. It exhibits a jump at the edge due to the onset of the Coster-Kronig vacancy transfer from the $L_1$ to the $L_3$ subshell. From the measured jump ratio 1.13±0.02 the Coster-Kronig yield $f_{13}$=0.49±0.09 is derived. This value agrees with a currently recommended value; however, it is significantly smaller than the prediction of recent relativistic calculations.