Elastic scattering and cluster-transfer reactions of 98Rb on 7Li at REX-ISOLDE

Exotic nuclei are nuclei with unusual proton to neutron ratios that exist far away from stability. Due to their instability, these nuclei are only available for nuclear reactions as radioactive ion beams. Experiments must therefore be performed in inverse kinematics at advanced radioactive isotope separation and acceleration facilities. REX-ISOLDE at CERN is one such facility, capable of producing post-accelerated radioactive ion beams with energies up to 2.85 MeV/u. Cluster-transfer reactions in inverse kinematics with a $^{7}$Li target are proposed as a tool for the study of exotic nuclei at REX-ISOLDE. In these reactions, either the $\alpha$ or triton clusters that make up the weakly bound $^{7}$Li nucleus can be transfered to the beam nucleus. The remaining cluster that is not transferred can be detected, and identifies the particular transfer channel. Through this mechanism it is possible to populate states of very high spin, which is useful for $\gamma$-spectroscopy in poorly known exotic regions. Specific regions of interest for these reactions are around doubly magic nuclei. Here adjacent nuclei are well described by valence nucleons interacting around the inert core. In particular the doubly magic $^{132}$Sn nucleus is also very neutron rich and serves as an ideal base from which to study changes in nuclear structure away from stability. Currently however, these very massive nuclei of interest are inaccessible to clustertransfer reactions with $^{7}$Li at REX-ISOLDE due to the high Coulomb barriers. In anticipation of the upgraded post-acceleration of HIE-ISOLDE that is currently being implemented, a preliminary experiment was performed with REX-ISOLDE to study the cluster-transfer reactions of the $^{98}$Rb + $^{7}$Li system. This experiment provides much needed experience and insight into the particularities of cluster-transfer with $^{7}$Li. Analysis performed for this masters thesis focused on the analysis of the detected particles. The elastic scattering channel was carefully treated to determine a scaling factor with which the absolute differential cross-sections for the detection of $\alpha$-particles and tritons could be scaled. The cross-sections for $\alpha$- and triton transfer were found to be larger than expected, boding well for future studies. The measured cross-sections were compared to theoretical calculations. A preliminary Continuum Discretized Coupled Channels (CDCC) calculation, which took into account the observation that the cluster transfer was occuring to high excitation unbound states, was able to reproduce well the data. Concerning the $\gamma$-rays, we indeed observed states of the residual nuclei at very high angular momenta. This thesis concludes with a discussion of the potential of cluster-transfer reactions going forward, in light of what we observe in this experiment. Important practical insights regarding the detection of particles are given and the possibilities for producing more exotic nuclei are given.