Discovery of the ${}^{151}$Eu $\alpha$ decay

We report on the first compelling observation of $\alpha$ 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$\pm 6.9(stat\mathrm{.})\pm 5.1(syst\mathrm{.})$ keV, and T${}_{1\mathrm{/}2}=(4.62\pm 0.95(stat\mathrm{.})\pm 0.68(syst\mathrm{.}))\times {10}^{18}$ y . The half-life prediction of nuclear theory using the Coulomb and proximity potential model are in good agreement with this experimental result.