Shape Changes in the Mirror Nuclei Kr 70 and Se 70

Abstract

We studied the proton-rich Tz=-1 nucleus Kr70 through inelastic scattering at intermediate energies in order to extract the reduced transition probability, B(E2;0+→2+). Comparison with the other members of the A=70 isospin triplet, Br70 and Se70, studied in the same experiment, shows a 3σ deviation from the expected linearity of the electromagnetic matrix elements as a function of Tz. At present, no established nuclear structure theory can describe this observed deviation quantitatively. This is the first violation of isospin symmetry at this level observed in the transition matrix elements. A heuristic approach may explain the anomaly by a shape change between the mirror nuclei Kr70 and Se70 contrary to the model predictions.