Relativistic Coulomb excitation of neutron-rich 54,56,58Cr: On the pathway of magicity from N=40 to N=32

Abstract The first excited 2 + states in 54,56,58 Cr were populated by Coulomb excitation at relativistic energies and γ rays were measured using the RISING setup at GSI. For 56 Cr and 58 Cr the B ( E2 , 2 1 + → 0 + ) values relative to the previously known B ( E 2 ) value for 54 Cr are determined as 8.7(3.0) and 14.8(4.2) W.u., respectively. The results are consistent with a subshell closure at neutron number N = 32 which was already indicated by the higher energy of the 2 1 + state in 56 Cr. Recent large-scale shell model calculations using effective interactions reproduce the trend in the excitation energies, but fail to account for the minimum in the B ( E 2 ) values at N = 32 .