Cluster-transfer reactions with radioactive beams: a spectroscopic tool for neutron-rich nuclei

In this thesis work, an exploratory experiment to investigate cluster-transfer reactions with radioactive beams in inverse kinematics is presented. The aim of the experiment was to test the potential of cluster-transfer reactions at the Coulomb barrier, as a possible mean to perform $\gamma$ spectroscopy studies of exotic neutron-rich nuclei at medium-high energies and spins. The experiment was performed at ISOLDE (CERN), employing the heavy-ion reaction $^{98}$Rb + $^{7}$Li at 2.85 MeV/A. Cluster-transfer reaction channels were studied through particle-$\gamma$ coincidence measurements, using the MINIBALL Ge array coupled to the charged particle Si detectors T-REX. Sr, Y and Zr neutron-rich nuclei with A $\approx$ 100 were populated by either triton- or $\alpha$ transfer from $^{7}$Li to the beam nuclei and the emitted complementary charged fragment was detected in coincidence with the $\gamma$ cascade of the residues, after few neutrons evaporation. The measured $\gamma$ spectra were studied in detail and the residue distributions were investigated as a function of the excitation energy and different spin distributions of the nuclei produced in the cluster-transfer process. Moreover, the reaction mechanism was qualitatively studied as a two-body process, considering the direct transfer of a cluster-like particle and using a Distorted Wave Born Approximation (DWBA). The results of this work show that cluster-transfer reactions can be well described as a direct process and that they could be considered for the population of neutron-rich nuclei at medium-high energies and spins. The same experimental technique can therefore be used in future experiments to study different exotic regions of the nuclides chart using radioactive ion beams of new generation.