First observation of rotational bands in the nucleus $$^{231}$$U

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($$\alpha $$ α ,5n) reaction at a beam energy of 52 MeV. Coincident decay $$\gamma $$ 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 $$\nu [633]5/2^{+}$$ ν [ 633 ] 5 / 2 + , yrast band $$\nu [752]5/2^{-}$$ ν [ 752 ] 5 / 2 - , and an excited band $$\nu [631]3/2^{+}$$ ν [ 631 ] 3 / 2 + . Configuration assignments are supported by Cranked Shell Model and B(M1)/B(E2) calculations. The excitation energy of the $$\nu [752]5/2^{-}$$ ν [ 752 ] 5 / 2 - bandhead is suggested to be 113.0 keV.