Z=50 Shell Gap Near Sn-100 From Intermediate-Energy Coulomb Excitations In Even-Mass Sn106-112 Isotopes

Rare isotope beams of neutron-deficient Sn-106,Sn-108,Sn-110 from the fragmentation of Xe-124 were employed in an intermediate-energy Coulomb excitation experiment. The measured B(E2, 0(1)(+) -> 2(1)(+)) values for Sn-108 and Sn-110 and the results obtained for the Sn-106 show that the transition strengths for these nuclei are larger than predicted by current state-of-the-art shell-model calculations. This discrepancy might be explained by contributions of the protons from within the Z = 50 shell to the structure of low-energy excited states in this region.