Measurement of theL2-L3Coster-Kronig transition probability in Tm(Z=69)

The $L_2$-$L_3$ Coster-Kronig transition probability ($f_{23}$) in Tm was measured by multiparameter K versus L x-ray coincidence techniques. The Tm x rays were obtained from a radioactive source of ${}_{}{}^{169}{}_{}{}^{}\mathrm{Yb}$ and were detected with cooled germanium and silicon detectors of high-energy resolution. Corrections were applied for the contribution of K${\alpha }_1$ x rays to the K${\alpha }_2$ x-ray peak and for the contribution of unresolved Lη x rays to the L${\alpha }_1$,2 x-ray peak. The contribution of K${\alpha }_1$ x rays to the K${\alpha }_2$ x-ray peak was determined solely from the results of the coincidence measurements using a method of data analysis which was previously described elsewhere. The contribution of Lη x rays to the L${\alpha }_1$,2 x-ray peak was determined from the coincidence measurements and published values of the Lη to L${\beta }_1$ x-ray intensity ratio. The result obtained for $f_{23}$ is (13.44±0.24)×${10}^{\mathrm{-}2}$ or (14.06±0.24)×${10}^{\mathrm{-}2}$ depending on the value of the Lη to L${\beta }_1$ intensity ratio used in applying the correction. Both values are slightly lower than predicted by the latest theoretical calculations confirming a trend of departures from theory recently observed in other medium- and high-Z atoms.