First observation of rotational bands in the nucleus ^231U

Abstract This work reports the first rotational bands observed in the neutron-deficient nucleus ^231 231 U. Excited states were populated in the ^232 232 Th (α, 5n) reaction at a beam energy of 52 MeV. Coincident decay γ -rays were measured with the high-purity germanium detectors of the afrodite spectrometer array, in conjunction with a recoil detector to discriminate against the fission background. The bands are interpreted as the ground-state band 6335/2^+ ν 633 5 / 2 +, yrast band 7525/2^- ν 752 5 / 2 -, and an excited band 6313/2^+ ν 631 3 / 2 +. Configuration assignments are supported by Cranked Shell Model and B (M 1) / B (E 2) calculations. The excitation energy of the 7525/2^- ν 752 5 / 2 - bandhead is suggested to be 113. 0 keV.