Probing the statistical decay and alpha-clustering effects in12C +12C and14N +10B reactions

An experimental campaign has been undertaken at Laboratori Nazionali di
Legnaro (LNL INFN), 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. On the experimental side, a first
reaction: 12C+12C at 95 MeV beam energy has been measured, using the GARFIELD +
Ring Counter (RCo) 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 alpha 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 alpha’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. In this perspective, 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.