Enhancement of B(E2) ↑ and low excitation of the second 0+ state near N=40 in Ge isotopes

The long-standing problem of dramatic structure change near N = 40 in Ge isotopes is investigated by means of large-scale shell model calculation. The analysis of simulated calculations suggests a possible understanding of the problem in terms of rapid increase in the g(9/2) proton and neutron occupation. The observed variation in excitation of the second 0(+) state in Ge-70,Ge-72,Ge-74 appears to correlate closely with the g(9/2) occupations induced by strong proton-neutron interactions. The enhancement of the g(9/2) occupancies is probably due to correlations in the 1g2d3s shell. (c) 2007 Elsevier B.V. All rights reserved.