Shape transitions far from stability: The nucleus 58Cr

Excited states up to Iπ = 8+ in the neutron-rich nucleus 58Cr have been identified by using a new experimental setup composed of the large acceptance magnetic spectrometer PRISMA and the highly efficient γ -detector array CLARA. Interestingly, the excitation energy sequence of the ground-state band follows the one expected by the E(5) dynamical symmetry for a nucleus at the critical point of the shape phase transition from a spherical vibrator (U(5)) to a γ -soft rotor (O(6)). For the first time, in the same physical system, large scale shell-model calculations in the full fp shell are compared to the E(5) analytical model results and to the Interacting Boson Model. The theoretical results are in excellent agreement with the present data.