Discovery of the ${}^{151}$Eu $\hat{I}\pm$ decay

Abstract

We report on the first compelling observation of $\hat{I}\pm$ decay of ${}^{151}$Eu to the ground state of ${}^{147}$Pm. The measurement was performed using a 6.15 g Li${}_6$Eu(BO${}_3$)${}_3$ crystal operated as a scintillating bolometer. The Q-value and half-life measured are: Q = 1948.9$\pm 6.9(stat.)\pm 5.1(syst.)$ keV, and T${}_{1/2}=\left(4.62\pm 0.95(stat.)\pm 0.68(syst.)\right)\times 10^{18}$ y . The half-life prediction of nuclear theory using the Coulomb and proximity potential model are in good agreement with this experimental result.