Investigation of the Spin cut-off Parameter of nuclear Level Density

The spin cut-off parameter has been investigated within the microscopic approach based on the BCS Hamiltonian. This parameter has been determined for a long range of even-even, odd-A and odd-odd, light, medium weight as well as heavy and spherical and deformed nuclei. The spin cut-off parameter $\sigma^{2}(E)$ has also be determined using the macroscopic methods and the results are compared with their corresponding microscopic values. It is found that the values of $\sigma^{2}$ at neutron binding energy $B_n$, show structure reflecting the shell model orbitals near the Fermi energy. The huge difference between $\sigma^{2}(B_n)$ deduced from the model calculations for nuclei near major shells indicates that the large angular momentum are responsible for their differences. In particular, the $1f_{7/2}$, $1g_{7/2}$ and $1i_{11/2}$ proton orbitals and the $1g_{9/2}$, $1h_{11/2}$ and $1i_{13/2}$ neutron orbitals play an important role in the $\sigma^{2}(B_n)$ values.