Possible Ground-State Octupole Deformation inPa229

Abstract

Evidence is presented for the occurrence of a ${\frac{5}{2}}^{\pm }$ parity doublet as the ground state of ${}_{}{}^{229}{}_{}{}^{}\mathrm{Pa}$, in agreement with a previous theoretical prediction. The doublet splitting energy is measured to be 0.22±0.05 keV. The relation of this doublet to ground-state octupole deformation is discussed.