Level widths and level densities in ²⁸Si, ⁴⁶Ti, ⁵²Cr, and ⁶⁰Ni from Ericson fluctuations

Ericson fluctuations in the differential cross sections were investigated for the compound reactions ²⁷Al(p,n₀)²⁷Si, ⁴⁵Sc(p,n₄)⁴⁵Ti, ⁴⁵Sc(p,n₅)⁴⁵Ti, ⁵¹V(p,n₀)⁵¹Cr, and ⁵⁹Co(p,n₀)⁵⁹Ni. Level widths in the compound nuclei ²⁸Si, ⁴⁶Ti, ⁵²Cr, and ⁶⁰Ni were extracted from the analysis of the differential cross sections by the Fourier method and a nonlinear fit to the ln⟨A_k²+B_k²⟩ distribution. The neutron spectra for each reaction were measured at least at three backward angles but the coherence width ⟨Γ⟩ did not show a strong angular dependence. Nuclear level densities for the above nuclei were extracted by relating the average level spacing D^Jπ to the average level width Γ^Jπ 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 ²⁸Si, ⁴⁶Ti, and ⁵²Cr but the comparison diverges for ⁶⁰Ni 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 δ=4.0, U<25 MeV, for ²⁸Si, a=4.8 and δ=−0.3, U<20 MeV, for ⁴⁶Ti, and a=4.8 and δ=0.3, U<20 MeV, for ⁵²Cr.