Nuclear level density parameter a has been calculated over a large range of nuclear mass and energy, using the microscopic model with the inclusion of nuclear pairing interaction. The values of a and the energy shift parameter $\delta ,$ appearing in the Bethe formula, are obtained by fitting the entropy as a function of excitation energy. Although the general behavior of $a,$ obtained with nuclear entropy is very similar to that of the conventional Fermi gas model, it shows deviations in the vicinity of major nuclear shells. The dependence of the level density parameter on energy has also been investigated and it is shown that the variation of a at lower energy is significant and has an asymptotic approach to a constant a at higher energies. The dependence of a on pairing force and deformation is illustrated.

• Received 2 January 2002

DOI:https://doi.org/10.1103/PhysRevC.66.064307