Proton emission from an oblate nucleus 151Lu

Excited states in the proton-unbound nucleus 151Lu have been established using γ-ray coincidence techniques. The lifetime of the first excited state above the proton-emitting ground state has been measured using the recoil-distance Doppler-shift method combined with recoil-decay tagging. The experimental level scheme and extracted lifetime have been compared with state-of-the-art theoretical calculations based upon a non-adiabatic deformed Woods-Saxon potential. This comparison suggests that the proton-emitting ground state in 151Lu is mildly oblate with a deformation β=−0.11−0.05+0.02 and represents the best evidence to date for proton emission from an oblate nucleus.