Nuclear Structure Of The Stable Even-A Calcium Isotopes Based On New Experiments And Shell Model Calculations

In view of the striking implications of the recently measured g factors for the 2(1)(+) states of Ca-42 and Ca-44 we have supplemented this study with similar measurements on Ca-46. For all three isotopes we utilized the powerful technique of projectile Coulomb excitation in inverse kinematics combined with transient magnetic fields. In contrast to the positive g(2(1)(+)) factor values for both Ca-42.44, implying large admixtures of particle-hole configurations from Ca-40 core excitations, the g factor of Ca-46(2(1)(+)), g=-0.19(12), is negative. This result is in very definite disagreement with the large positive value predicted by the large scale shell model (LSSM) calculations which included sd shell core excitations into the fp shell and accounted well for corresponding Ca-42,Ca-44 results. The B(E2;0(1)(+)-->2(1)(+)) deduced from the remeasured Ca-46(2(1)(+)) lifetime is indeed substantially smaller than the corresponding value for Ca-42, again contrary to LSSM predictions. Both g(2(1)(+)) and B(E2) in Ca-46 can be explained by full fp shell model calculations using the FPD6 interaction without invoking core excitations.