Enhanced collectivity in 74Ni

The neutron-rich nucleus Ni-74 was studied with inverse-kinematics inelastic proton scattering using a Ni-74 radioactive beam incident on a liquid hydrogen target at a center-of-mass energy of 80 MeV. From the measured de-excitation gamma rays, the population of the first 2(+) state was quantified. The angle-integrated excitation cross section was determined to be 14(4) mb. A deformation length of delta = 1.04(16) fm was extracted in comparison with distorted wave theory, which suggests that the enhancement of collectivity established for Ni-70 continues up to Ni-74. A comparison with results of shell model and quasi-particle random phase approximation calculations indicates that the magic character of Z = 28 or N = 50 is weakened in Ni-74. (C) 2010 Elsevier B.V. All rights reserved.