Configuration mixing and relative transition rates between low-spin states in 68Ni

The low-spin level scheme of Ni-68 was investigated following two-neutron-knockout and multinucleon-transferreactions. The energy of the first excited state was determined to be E-x(0(2)(+)) = 1603.5(3) keV. Relative B(E2) transition probabilities were deduced and compared with shell-model calculations using several modern effective interactions. Theory reproduces the data well, but indicates substantial mixing of multi-particle, multi-hole configurations for the lowest observed 0(+) and 2(+) states.