Angular momentum dependence of the nuclear level density in theA≈170–200 region

Abstract

Neutron evaporation spectra along with $\ensuremath{\gamma}$ multiplicity has been measured from $^{201}\mathrm{Tl}{}^{*},^{185}\mathrm{Re}{}^{*}$, and $^{169}\mathrm{Tm}{}^{*}$ compound nuclei at the excitation energies of $\ensuremath{\sim}27$ and 37 MeV. Statistical model analysis of the experimental data has been carried out to extract the value of the inverse level density parameter $k$ at different angular-momentum $(J)$ regions corresponding to different $\ensuremath{\gamma}$ multiplicities. It is observed that, for the present systems the value of $k$ remains almost constant for different $J$. The present results for the angular-momentum dependence of the nuclear level density (NLD) parameter $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{a}\phantom{\rule{4pt}{0ex}}(=A/k)$, for nuclei with $A\ensuremath{\sim}180$ are quite different from those obtained in earlier measurements in the case of light- and medium-mass systems. The present study provides useful information to understand the angular-momentum dependence of the NLD at different nuclear mass regions.