Coulomb excitation of Ca 44 and Ar 46

The reduced transition probabilities B(E2; 0(g.s.)(+) -> 2(1)(+)) of the Ar-46 and Ca-44 nuclei were studied using the Coulomb excitation technique at intermediate energy at the LISE/GANIL facility. The in-flight gamma rays, emitted after the Coulomb excitation of their first 2(+) states, were detected in an array of 64 BaF2 crystals. The present B(E2 up arrow) value for Ca-44, 475(36) e(2)fm(4), agrees well with the value of 495(35) e(2)fm(4) obtained by averaging results of previous experiments. Consistent B(E2; 0(g.s.)(+) -> 2(1)(+)) values of 225(29) e(2)fm(4) and 234(19) e(2)fm(4) have been obtained for Ar-46 from an absolute and a relative measurement, normalized to the Ca-44 value. Both results agree with the ones obtained with the same experimental technique at the NSCL facility but are a factor of 2 smaller than the shell model predictions. The drop in B(E2; 0(g.s.)(+) -> 2(1)(+)) in the Ar chain at N = 28, confirmed in this experiment, shows that Ar-46 is sensitive to the N = 28 shell closure.