Evidence for spherical-oblate shape coexistence in Tc 87

Abstract

Excited states in the neutron-deficient nucleus Tc87 have been studied via the fusion-evaporation reaction Fe54(Ar36,2n1p)Tc87 at 115 MeV beam energy. The AGATA γ-ray spectrometer coupled to the DIAMANT, NEDA, and Neutron Wall detector arrays for light-particle detection was used to measure the prompt coincidence of γ rays and light particles. Six transitions from the deexcitation of excited states belonging to a new band in Tc87 were identified by comparing γ-ray intensities in the spectra gated under different reaction channel selection conditions. The constructed level structure was compared with the shell model and total Routhian surface calculations. The results indicate that the new band structure in Tc87 is built on a spherical configuration, which is different from that assigned to the previously identified oblate yrast rotational band.