8Be cluster emission versus alpha evaporation in 28Si + 12C

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The possible occurence of highly deformed configurations in the ⁴⁰Ca di-nuclear system formed in the ²⁸Si + ¹²C reaction is investigated by analyzing the spectra of emitted light charged particles. Both inclusive and exclusive measurements of the heavy fragments (A ≥ 10) and their associated light charged particles (protons and α particles) have been made at the IReS Strasbourg VIVITRON Tandem facility at bombarding energies of Elab (²⁸Si) = 112 MeV and 180 MeV by using the ICARE charged particle multidetector array. The energy spectra, velocity distributions, in-plane and out-of-plane angular correlations of light charged particles are compared to statistical-model calculations using a consistent set of parameters with spin-dependent level densities. This spin dependence approach suggests the onset of large nuclear deformation in ⁴⁰Ca at high spin. This conclusion might be connected with the recent observation of superdeformed bands in the ⁴⁰Ca nucleus. The analysis of α particles in coincidence with ³²S fragments suggests a surprisingly strong ⁸Be cluster emission of a binary nature.