One-nucleon transfer reactions induced by secondary beam of 11Be: study of the nuclear structure of the exotic nuclei 11Be and 10Li

The structure of the neutron rich light nuclei 11Be and 10Li has been investigated by means of one nucleon transfer reactions. The experiments have been carried out at GANIL in inverse kinematics using 11Be secondary beams. The 11Be(p,d)10Be reaction bas been studied at 35.3 MeV/u. The 10Be ejectiles were analyzed by the spectrometer SPEG, and coincident deuterons were detected in the position sensitive silicon detector CHARISSA. Transfer cross sections to 0+1 and 2+1, states in 10Be were measured up to θCM = 16 deg. and compared to DWBA and CRC predictions. The effects of neutron-cure couplings on reaction form factors have been studied by solving coupled equations in the framework of a vibrational model. It is shown that the rate of core excitation 10Be2+ in the 11Begs wave function is overestimated by a standard analysis with form factors given by the usual Separation Energy prescription. The former model predicts a rate of core excitation of 16% and leads to theoretical cross sections which are in good agreement with the experimental data. The aim of the 11Be(d,3He)10Li experiment, realized at 37 MeV/u, was to measure the distribution of the 2s neutron strength in the unbound nucleus 10Li. The energy spectrum was deduced from the 3He energy and angle measured by the silicon strip detector array MUST. An asymmetric peak is clearly observed near the threshold, with a maximum at -Sn = 130 keV. This constitutes a direct proof of the inversion of 2s and 1p1/2 shells in 10Li, which was until now a controversial question in spite of many experimental efforts. On the other band the analysis of the 11Be(d,t)10Be reaction studied in the same experiment confirms the results obtained in the 11Be(p,d)10Be reaction concerning the 11Begs structure. This work shows the interest and feasibility of studies of the shell properties of exotic nuclei using transfer reactions induced by radioactive beams and constitutes the beginning of a program devoted to this kind of experiment. (author)