Pre-equilibrium emission and its possible relation to α-clustering in nuclei

The study of nuclear states built on clusters bound by valence neutrons in their molecular configurations is a field of large interest. Clustering becomes particularly important at the dripline, where weakly bound systems prevail. For light nuclei, at an excitation energy close to the particle separation value, there are experimental evidences of such structure effects, but this is still not the case for heavier nuclear systems. Several theoretical efforts have been done in the development of pre-formation alpha-clustering models, but there is still a lack of experimental data capable to give a direct feedback. The search of alpha-cluster evidences in medium-mass systems is therefore a new challenge which can give new hints in this field of research. In the past we have studied the reactions 250, 192 and 130 MeV O-16 + Sn-116, observing a significant increase in the fast emitted alpha-particle yield. This effect was ascribed to the presence of pre-formed alpha-clusters in the 16O projectile nucleus. To further investigate these aspects in a model independent way, a new experimental campaign has been performed with the GARFIELD + RCo set up. Two different reaction entrance channels (O-16 and F-19) at the same beam velocity (16AMeV) have been measured, leading to the same Rb-81* compound nucleus. In this contribution we report on the preliminary light-charged particles emission spectra obtained in coincidence with evaporation residues and their comparison with the results obtained from a Hybrid Exciton Model calculation.