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 γ-ray multiplicities have been measured around A ≈ 110 in the 16 O, 20 Ne + 93 Nb reactions in a compound nuclear excitation energy range of ≈ 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 γ-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.