Excitation energy and angular momentum dependence of the nuclear level density parameter around A$\approx$110

Abstract

Neutron kinetic energy spectra in coincidence with low-energy ${\hat{I}}^3$-ray multiplicities have been measured around $A\approx$ 110 in the ${}^{16}$O, ${}^{20}$Ne + ${}^{93}$Nb reactions in a compound nuclear excitation energy range of $\approx$ 90 - 140 MeV. The excitation energy (temperature) and angular momentum (spin) dependence of the inverse level density parameter $k$ has been investigated by comparing the experimental data with statistical Hauser-Feshbach calculation. In contrast to the available systematic in this mass region, the inverse level density parameter showed an appreciable increase as a function of the excitation energy. The extracted $k$-values at different angular momentum regions, corresponding to different ${\hat{I}}^3$-multiplicities also showed an overall increase with the average nuclear spins. The experimental results have been compared with a microscopic statistical-model calculation and found to be in reasonable agreement with the data. The results provide useful information to understand the variation of nuclear level density at high temperature and spins.