Neutron induced reactions of $^{150}$Sm and influence of spin distribution in the pre-equilibrium process*

Cross-section measurements were made of prompt $\gamma$-ray production as a function of incident neutron energy (E$_n$ = 1 to 35 MeV) on an enriched (95.6$\%$) $^{150}$Sm sample. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the Los Alamos Neutron Science Center facility. The prompt-reaction $\gamma$ rays were detected with the large-scale Compton-suppressed Germanium Array for Neutron Induced Excitations (GEANIE). Neutron energies were determined by the time-of-flight technique. The preequilibrium reaction process is important at high energies. The spin distribution transferred in preequilibrium neutron-induced reactions was calculated using the quantum mechanical theory of Feshbach, Kerman, and Koonin (FKK). These preequilibrium spin distributions were incorporated into a new version of the Hauser-Feshbach statistical reaction code GNASH and the $\gamma$-ray production cross sections were calculated and compared with experimental data. The difference in the partial $\gamma$-ray cross sections using spin distributions with and without preequilibrium effects will be discussed.