Ericson fluctuations in the differential cross sections were investigated for the compound reactions ${}^{27}\mathrm{Al}(p,n_0){}^{27}\mathrm{Si}$, ${}^{45}\mathrm{Sc}(p,n_4){}^{45}\mathrm{Ti}$, ${}^{45}\mathrm{Sc}(p,n_5){}^{45}\mathrm{Ti}$, ${}^{51}\mathrm{V}(p,n_0){}^{51}\mathrm{Cr}$, and ${}^{59}\mathrm{Co}(p,n_0){}^{59}\mathrm{Ni}$. Level widths in the compound nuclei ${}^{28}\mathrm{Si}$, ${}^{46}\mathrm{Ti}$, ${}^{52}\mathrm{Cr}$, and ${}^{60}\mathrm{Ni}$ were extracted from the analysis of the differential cross sections by the Fourier method and a nonlinear fit to the $\ln ⟨A_k^2+B_k^2⟩$ distribution. The neutron spectra for each reaction were measured at least at three backward angles but the coherence width $⟨\Gamma ⟩$ did not show a strong angular dependence. Nuclear level densities for the above nuclei were extracted by relating the average level spacing $D^{J\pi }$ to the average level width ${\Gamma }^{J\pi }$ using the fluctuation theory. Reasonable agreements were found with other level densities and level density compilations based in the Fermi gas formalism of Al-Quraishi and Huang for ${}^{28}\mathrm{Si}$, ${}^{46}\mathrm{Ti}$, and ${}^{52}\mathrm{Cr}$ but the comparison diverges for ${}^{60}\mathrm{Ni}$ for which additional measurements are required in order to clarify the observed discrepancies. The level density parameters that best describe the data are $a=3.5$ and $\delta =4.0$, $U<25\mathrm{MeV}$, for ${}^{28}\mathrm{Si}$, $a=4.8$ and $\delta =-0.3$, $U<20\mathrm{MeV}$, for ${}^{46}\mathrm{Ti}$, and $a=4.8$ and $\delta =0.3$, $U<20\mathrm{MeV}$, for ${}^{52}\mathrm{Cr}$.

• Received 4 March 2004

DOI:https://doi.org/10.1103/PhysRevC.70.024311