First measurement of the partial widths of $^{209}$Bi decay to the ground and to the first excited states

摘要

$^{209}$Bi alpha decay to the ground and to the first excited state have beencontemporary observed for the first time with a large BGO scintillatingbolometer. The half-life of $^{209}$Bi is determined to be$\tau_{1/2}$=(2.01$\pm$0.08)$\cdot10^{19}$ years while the branching ratio forthe ground-state to ground-state transition is (98.8$\pm$0.3)%.