Mixed-symmetry octupole and hexadecapole excitations in the N=52 isotones
Abstract
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 92Zr and 94Mo. Purpose: The heaviest stable N=52 isotone 96Ru was investigated to study the evolution of octupole and hexadecapole MSS with increasing proton number. Methods: Two inelastic proton-scattering experiments on 96Ru 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 96Ru. 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.