KandLShakeoff Probability inSm151

Abstract

We have measured the $K$-electron-emission probability for the 76-keV $\ensuremath{\beta}$ decay of $^{151}\mathrm{Sm}$ and obtain ${P}_{K}=(2.4\ifmmode\pm\else\textpm\fi{}0.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. We correct an earlier measurement to ${P}_{K}=(2.3\ifmmode\pm\else\textpm\fi{}0.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. From the agreement with the Law-Campbell shakeoff-plus-shakeup prediction, 2.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$, the direct collision contribution to the $K$ emission is limited to $\ensuremath{\sim}\frac{1}{3}$ of the Feinberg prediction, contrary to recent claims. We obtain an $L$---x-ray probability due to $L$-electron shakeoff per $\ensuremath{\beta}$ decay of (5.4\ifmmode\pm\else\textpm\fi{}1.0) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$, about half the theoretical value, and also some indication that $L$ shakeoff is predominantly ${L}_{1}$.