Nuclear Level Densities and Reaction Mechanisms from Continuum Neutron Spectra

The neutron spectra produced by the ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}\mathrm{}(p,n)\mathrm{}{}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}\mathrm{}(p,n)\mathrm{}{}_{}{}^{59}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}(\alpha ,n){}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$, and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}(\alpha ,n){}_{}{}^{59}{}_{}{}^{}\mathrm{Ni}$ reactions were measured at five angles between 15 and 135° for proton energies between 7.8 and 14.7 MeV, and for $\alpha$ energies between 11.5 and 22.7 MeV. Spectra at low energies were used to obtain the spin-weighted level density of the residual nuclei ${}_{}{}^{51}{}_{}{}^{}\mathrm{Cr}$ and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Ni}$. Comparison of these spectral shapes with those obtained at higher energies made possible a separation of the higher-energy spectra into compound and noncompound contributions.