Decay of excited medium-mass compound nuclei

Abstract

An experimental campaign has been performed by the NuclexHector collaboration at the Laboratori Nazionali di Legnaro in order to study different reaction channels by detecting, in coincidence, Evaporation Residue (ER), Charged Particles and high energy γ-rays from Giant Dipole Resonance (GDR). The studied system was 48 Ti+ 40 Ca at 300, 450 and 600 MeV, using a modular apparatus formed by triplephoswich detectors for ER and particles at the forward angles, the GARFIELD ΔE-E forward drift chamber for the charged particles between 30 o and 85 o and the HECTOR apparatus at the backward angles for γ-rays. Hot rotating nuclei in the region A=100 formed via fusion reactions have different de-excitation modes, from nucleon evaporation to fission and GDR emission. The study of this modes is interesting for the knowledge of the relaxation of both intrinsic and collective degrees of freedom, opening also new possibilities in view of future experiments with exotic beams. The present work was done with the aim to investigate in a rather complete and exclusive way the several decay processes of the 88 Mo Compound Nucleus (CN), formed in fusion reactions between 48 Ti and 40 Ca at 300, 450 and 600 MeV. A large part of the reaction cross section for these reactions is exhausted by fusion. At these three energies, for full momentum transfer, we produce CN with an excitation energy of 126, 194 and 262 MeV respectively and with spin arriving at the critical values for fission (l∼65-70 ¯). Decay of 88 Mo can occur via particle evaporation and fission (symmetric or asymmetric).