An experimental investigation of the 15.1 keV M1 + E2 nuclear transition in 227Th from the $\beta^{-}$ decay of 227Ac

Abstract

Using the internal conversion electron spectroscopy, the energy of the 15.1 keV $ M1+E2$ nuclear transition in 227Th populated in the $ \beta^{-}$ decay of 227Ac was determined to be $ 15098.6 \pm 1.0$ eV. This value is more accurate than the present accepted one by a factor of 200. The present uncertainty in the transition multipolarity was removed and it was found to be $ M1+E2$ with the admixture $ \vert\delta (E2/M1)\vert = 0.035 \pm 0.006$.