Microscopic study of Nuclear Spin Cut-off Parameter*

Spin cut-off parameter and effective moment of inertia have been investigated within the microscopic approach based on BCS- Hamiltonian. The spin cut-off parameter has been calculated at neutron binding energies over a large range of nuclear mass A, using the BCS theory. The results are compared with their corresponding macroscopic values. It is found that the values of $_{ }\sigma ^{2}$ (E) do not increase smoothly with A as expected based on macroscopic theory. Instead, the values of $\sigma ^{2}$ (E) shows structure reflecting the angular momentum of the shell model orbitals near the Fermi energy. The spin cut-off parameter $\sigma ^{2}$ (E) has also been computed from the knowledge of nuclear level density, at neutron binding energy, B$_{n }$and the average S-wave neutron spacing, $\sigma ^{2}$ = 1/2$\rho $(B$_{n})<$D$_{1/2}>$ . These are also compared with their corresponding values from the model calculations. The results will be presented and discussed.