αclustering effects in 12C+12C and 14N+10B reactions at 2.6 A.MeV excitation energy

An experimental campaign has been undertaken at Laboratori Nazionali di Legnaro, Italy, in order to progress in our understanding of the statistical properties of light nuclei at excitation energies above particle emission threshold, by measuring exclusive data from fusion evaporation reactions. These properties notably include the excitation energy dependence of the nucleon effective mass, symmetry energy and pairing correlations. In particular, the determination of the nuclear level density in the A∼ 20 region, the understanding of the statistical behaviour of light nuclei with excitation energies∼3 A.MeV, and the measurement of observables linked to the presence of cluster structures of nuclear excited levels are the main physics goals of this work. On the experimental side, a first reaction: 12C+12C at 95 MeV beam energy has been measured, using the Garfield + Ring Counter (R Co) apparatuses]. Fusion-evaporation events have been exclusively selected out of the entire data set. The comparison to a dedicated Hauser-Feshbach calculation allows us to give constraints on the nuclear level density at high excitation energy for light systems ranging from C up to Mg. Out- of-equilibrium emission has been evidenced and attributed both to an entrance channel effect (favoured by the cluster nature of reaction partners), and, in more dissipative events, to the persistence of cluster correlations well above the 24Mg threshold for 6 α s decay. In order to study the same 24Mg compound nucleus at similar excitation energy with respect to this first reaction a new measurement, 14N + 10B at 5.7 A.MeV, was performed at LNL laboratories with the same experimental setup. The comparison between the two systems would allow us to further constrain the level density of light nuclei in the mass-excitation energy range of interest. Deviations from a statistical behaviour can be used as a tool to get information on nuclear clustering, both in the ground-state for projectile and target and in the hot source formed in the collision