  The $\Theta_{eff}/\Theta_{rig}$ parameter of the spin distribution of the
level density was determined for 61 nuclei covering the mass range of 44 to
200. The experimental isomeric cross-section ratios for 25 isomeric pairs were
compared with the model calculation to find the best fit to the experimental
data. The model calculations were carried out with the TALYS code using the
BSFG model for the level density. The reduced $\chi ^2$ values were calculated
to describe the deviation of the experimental data from the model calculation.
An $\eta_d $ was introduced calculating the $\Theta_{eff}/\Theta_{rig}$ value
from the low energy discrete levels of the nucleus. The $\eta /\eta_d $ values
seem to be independent of the mass number, their average value near to one. The
$\eta /\eta_d $ values also seem to be independent of the average excitation
energy in the continuum, indicating that $\eta $ is independent of the
excitation energy. The mass number and (N-Z) dependence of the $\eta $ values
were studied. The $\eta $ values for the nuclei with odd mass number show an
exponential decrease as a function of A or (N-Z). The $\eta $ values for the
odd-odd type of nuclei appear to be constant, near one, up to the mass number
110 or (N-Z) of 13. Above these values, the $\eta $ values show exponential
decrease. The $\eta $ values for even-even type nuclei decrease exponentially
up to A equal to 142 or (N-Z) equal to 20. The values are lower than those for
the nearby odd-odd type nuclei. The $\eta $ values increase for nuclei with A
between 142 and 156 and (N-Z) between 20 and 28, and they finally reach the
value of odd-odd type systematics.
