Experiments on multiphonon states with proton–neutron mixed symmetry in vibrational nuclei

Considerable progress has been achieved in the experimental investigation and theoretical understanding of isovector valence shell structures in heavy nuclei that are frequently called mixed-symmetry states. This article attempts a review of the experimental aspects and data on mixed-symmetry states of vibrational and weakly deformed transitional nuclei. After a brief introduction the main experimental tools are described that have lately been used for the investigation of mixed-symmetry states in vibrational and transitional nuclei. The main body reviews the available data where the mixed-symmetry assignments have been made on the basis of large magnetic dipole transition rates.