Octupole strength in the neutron-rich calcium isotopes
  Low-lying excited states of the neutron-rich calcium isotopes $^{48-52}$Ca have been studied via $\gamma$-ray spectroscopy following inverse-kinematics proton scattering on a liquid hydrogen target using the GRETINA $\gamma$-ray tracking array. The energies and strengths of the octupole states in these isotopes are remarkably constant, indicating that these states are dominated by proton excitations. 
L. A. Riley, D. M. McPherson, M. L. Agiorgousis, T. R. Baugher, D.   Bazin, M. Bowry, P. D. Cottle, F. G. DeVone, A. Gade, M...
nucl-ex