Mixed-symmetry octupole and hexadecapole excitations in N=52 isotones (original) (raw)

Background: Excitations with mixed proton-neutron symmetry have been previously observed in the N = 52 isotones. Besides the well-established quadrupole mixed-symmetry states (MSS), octupole and hexadecapole MSS have been recently proposed for the nuclei 92 Zr and 94 Mo. Purpose: The heaviest stable N = 52 isotone 96 Ru was investigated to study the evolution of octupole and hexadecapole MSS with increasing proton number. Methods: Two inelastic proton-scattering experiments on 96 Ru were performed to extract branching ratios, multipole mixing ratios, and level lifetimes. From the combined data, absolute transition strengths were calculated. Results: Strong M1 transitions between the lowest-lying 3 − and 4 + states were observed, providing evidence for a one-phonon mixed-symmetry character of the 3 (−) 2 and 4 + 2 states. Conclusions: sdg-IBM-2 calculations were performed for 96 Ru. The results are in excellent agreement with the experimental data, pointing out a one-phonon hexadecapole mixed-symmetry character of the 4 + 2 state. The 3 − 1 ||M1||3 (−) 2 matrix element is found to scale with the 2 + s ||M1||2 + ms matrix element.