The light charged particles emitted from hot ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ compound nuclei, populated at excitation energy ${\mathit{E}}_{\mathit{x}}$=94 MeV and 〈J〉=20.5ħ by the reaction 130 MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ on ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, have been studied. Energy spectra of protons and alpha particles, measured in coincidence with evaporation residues and with a selection of multiple-alpha chains, have been compared with the predictions of Monte Carlo statistical model calculations. The comparison shows that the level density of hot nuclei with A≤40, needed to account for the measured quantities, is well predicted by the Fermi-gas model using a level-density parameter ${\mathit{a}}_{\mathrm{eff}}$=A/8 ${\mathrm{MeV}}^{\mathrm{-}1}$ up to excitation energy 〈${\mathit{E}}_{\mathrm{th}}$/A〉∼1.7 MeV. In agreement with theory, light hot nuclei do not show the transition from ${\mathit{a}}_{\mathrm{eff}}$=A/8 ${\mathrm{MeV}}^{\mathrm{-}1}$ to ${\mathit{a}}_{\mathrm{eff}}$∼A/13 ${\mathrm{MeV}}^{\mathrm{-}1}$ evidenced in the A∼160 mass region for the same range of excitation energies ${\mathit{E}}_{\mathrm{th}}$/A. The analysis of the alpha-particle spectra shows that the effects associated with the angular-momentum-induced deformations depend on the entrance channel characteristics and, in this case, are very small compared with those evidenced in the past for compound nuclei in the region A=50–70.

• Received 22 July 1991

DOI:https://doi.org/10.1103/PhysRevC.44.2588