Effective Charges in Nuclei in the vicinity of 100Sn

Abstract: The shell structure of atomic nuclei far from the line of beta-stability and the properties of the nucleon-nucleon interaction in exotic isotopes are not well known. The development of radioactive ion beams (RIBs) puts certain unexplored regions of the nuclear chart within reach of detailed experimental investigations. The low-energy nuclear structure of the unstable isotopes 106,108,110Sn, 100,102,104Cd, and 106,108In have been studied using sub-barrier Coulomb excitation of postaccelerated RIBs. The experiments were carried out at the REX-ISOLDE facility at CERN. The deduced transition probabilities - B(E2) values - provide a detailed benchmark of modern models of the nucleon-nucleon interaction. The B(E2) values between the 0+ ground states and the first excited 2+ states in the Sn and Cd isotopes were compared with shell-model calculations. These are based on effective interactions derived from renormalized multi-meson and QCD-based nucleon-nucleon potentials. In order to reproduce the experimental results in the calculations, the neutron effective charge requires a renormalization. The observed effect is most prominent in the light Sn isotopes. The static quadrupole moments - Q(2+) values - of the first excited 2+ states in the 102Cd and 104Cd isotopes were measured using the reorientation effect in Coulomb excitation. In this approach, the B(E2) and Q(2+) values of each isotope are correlated. Therefore, the collected data were analyzed using the maximum likelihood method. In this way, the two-dimensional probability distributions could be determined. In turn, this enables a detailed comparison with theoretical models. Here, the results were interpreted using the shell-model. The observed gamma-ray de-excitation patterns in 106,108In were also interpreted in the shell-model. The excited states in 108In were further analyzed in terms of their proton-neutron multiplet character.