Level density and thermodynamics in the hot rotating Tc96 nucleus

Abstract

Evaporated neutron energy spectra have been measured in coincidence with low-energy discrete $\ensuremath{\gamma}$ rays in the reaction $^{4}\mathrm{He}+^{93}\mathrm{Nb}$ at $E(^{4}\mathrm{He})=28$ MeV. The low-energy light-ion beam provides the scope of extracting the experimental nuclear level density (NLD) in the compound nuclear reaction. Angular-momentum gated NLDs have been extracted in the excitation energy range of ${E}^{*}\ensuremath{\sim}5--15$ MeV from the measured neutron energy spectra. The extracted NLDs have been compared with different theoretical calculations such as the exact pairing plus independent particle model at finite temperature (EP+IPM), Hartree-Fock plus BCS (HFBCS), and Hartree-Fock-Bogoliubov plus combinatorial method (HFBC). Interestingly, the experimental NLDs are in good agreement with the results of the EP+IPM, whereas the HFBCS and HFBC fail to describe these data. Consequently, the thermodynamic properties of $^{96}\mathrm{Tc}$ at finite angular momentum have been extracted using the EP+IPM NLDs. Through the analysis of the calculated thermodynamic quantities, it is shown that no pronounced bump is seen in the heat capacity of $^{96}\mathrm{Tc}$, in opposition with the earlier results of $^{96}\mathrm{Mo}$, which showed a prominent bump at $T\ensuremath{\sim}0.7--1$ MeV. This difference is understandable since pairing in the even-even system ($^{96}\mathrm{Mo}$) is always stronger than that in the odd-odd one ($^{96}\mathrm{Tc}$).