Coulomb excitation and structure of the rotational bands in 231Pa Original Research Article

The level structure of 231Pa was investigated by Coulomb excitation using 148 MeV 32S and 255, 260 and 261 MeV 58Ni projectiles and the NORDBALL detector array. The 1/2[530] ground-state rotational band was excited up to spin 39/2−. The 3/2[651] band, established up to spin 37/2+, was observed to be populated apart from direct Coulomb excitation by the de-excitation of the 1/2[530] band. The 1/2[400] band could be followed up to spin 23/2+. Weak excitation of the bands 5/2[642], 5/2[512], 3/2[532] and 3/2[521] was seen up to spins 11/2+, 15/2−, 9/2− and 9/2−, respectively. Matrix elements were extracted from the γ-ray yields with the help of the semi-classical Coulomb-excitation least-squares search code GOSIA. The level scheme and transition intensities were analyzed in the framework of the quasiparticle-plus-phonon model including Coriolis-coupling (QPMC).