209Bi level calculation

209Bi has recently observed to α-decay with scintillating bolometer, to the ground state (GS) and to first the excited state (ES). although of the belief it was a stable nuclei. Even previous measurement observed the decay, but only the GS-GS transition. This decay belongs to a special class of decays occurring in odd-A nuclei with an extra nucleon outside a closed shell. 209Bi alpha decay branching ratios (BR) to the ground and to two different excited states were numerically evaluated. While the BR for the ground-state decay is well known, the calculation for the excited states was performed for the first time. Even if the used model is a simplified theory (not strictly correct for deformed nuclei), it gives a good estimate of the decay half life.