Quadrupole collectivity beyond N=28: Intermediate-energy Coulomb   excitation of 47,48Ar
  We report on the first experimental study of quadrupole collectivity in the very neutron-rich nuclei \nuc{47,48}{Ar} using intermediate-energy Coulomb excitation. These nuclei are located along the path from doubly-magic Ca to collective S and Si isotopes, a critical region of shell evolution and structural change. The deduced $B(E2)$ transition strengths are confronted with large-scale shell-model calculations in the $sdpf$ shell using the state-of-the-art SDPF-U and EPQQM effective interactions. The comparison between experiment and theory indicates that a shell-model description of Ar isotopes around N=28 remains a challenge. 
R. Winkler, A. Gade, T. Baugher, D. Bazin, B. A. Brown, T. Glasmacher,   G. F. Grinyer, R. Meharchand, S. McDaniel, A. Ratki...
nucl-ex nucl-th