Transfer reactions in inverse kinematics at REX-ISOLDE

Doktorsavhandling, 2009

Research on the structure of exotic nuclei is one of the most intriguing topics in present day nuclear physics. With the use of facilities for isotope separation on-line, such as ISOLDE at CERN, short-lived isotopes can be studied experimentally. Since 2002, the REX-ISOLDE facility enables radioactive ions produced by ISOLDE to be post-accelerated, increasing the energy of the ions enough to do nuclear transfer reactions in inverse kinematics. In this thesis, transfer reactions are used to study the structure of neutron-rich lithium isotopes through a series of experiments at REX-ISOLDE. The first experiment used a 9Li beam at 2.36 MeV/u impinging on a deuterated polyethylene target to study 10Li, 9Li and 8Li. For the (d,p)-channel the resonance ground state and a first excited state are observed and the results agree with theoretical calculations. The elastic channel agrees with Optical Model, OM, calculations. For the (d,t)-channel the shape of the angular distribution agrees with Distorted Wave Born Approximation, DWBA, calculations but the absolute scale is not reproduced. Therefore, a benchmark experiment with an 8Li beam at 3.15 MeV/u on the same target was made to test the validity of the method. Using OM calculations with the same potentials as for the 9Li experiment, the data from the elastic channel and OM agree on an absolute scale. The (d,p)-channel is well described for small scattering angles using DWBA calculations; the agreement extends to even larger angles if coupled-channels are taken into account. The conclusion is that transfer reactions remain a viable tool for investigating nuclear structure. Beyond the need to improve experimental obstacles such as increasing the beam energy, the analysis highlights the need of careful modelling of the reaction mechanism to be able to describe the data. The obtained results give confidence to investigate even more exotic nuclei and also to search for resonance states in unbound nuclei. The general analysis and simulation programs developed will be applicable for future experiments.