Isovector Quadrupole Excitations in the Valence Shell of Vibrational Nuclei

Coulomb excitation experiments in inverse kinematics of stable ions impinging on a carbon target at energies of about 85 % of the respective Coulomb barriers have been performed in the A similar to 130 region. Proton-neutron mixed-symmetry one-quadrupole phonon state 2(1,ms)(+) has been identified in several nuclides from the large B(M1; 2(1,ms)(+) -> 2(1)(+)) value as compared to typical M1 strengths between low-energy 2(+) states. As an example, we focuss on the evolution of the 2(1,ms)(+) state in the N=80 isotonic chain. The local proton-neutron quadrupole-quadrupole interaction strength is determined from these data within a schematic two-state mixing model.