Level Density of Light Nuclei

The level density of light nuclei (A≤70) is studied by analyzing statistical reaction spectra, slow-neutron resonances, and level widths at high excitation energy. Further evidence seems to indicate that, as proposed in a preceding work, the effective excitation energy of excited nuclei, appearing in the Lang-Le Couteur level-density formula, must be calculated by means of the following expression: U=(E-Δ+70/A) E is the usual excitation energy, Δ is the pairing energy, and 70/A MeV is a term that shifts, in a smooth manner, the zero of the energy scale of different nuclei. In this case the Lang-Le Couteur formula, assuming R1.5A1/3 F, I=0.7Irig, $a=(0.127A)$ MeV^-1, gives, without further changes of its parameters, a correct estimation of the slope and absolute value of the level densities of light nuclei for energies ranging from (1+Δ) up to {~}20 MeV. It is also shown that the preceding choice of the parameters of Lang-Le Couteur level-density expression allows one to reproduce very well the experimental distributions of low-energy levels observed with reactions which proceed, at least partially, through the formation of a compound nucleus.