Microscopic structure of high-spin vibrational excitations in superdeformed ^190,192,194Hg

Microscopic calculations based on the cranked shell model extended by the random-phase-approximation are performed to investigate the quadrupole and octupole correlations for excited superdeformed bands in ¹⁹⁰Hg, ¹⁹²Hg, and ¹⁹⁴Hg. The K=2 octupole vibrations are predicted to be the lowest excitation modes at zero rotational frequency. At finite frequency, however, the interplay between rotation and vibrations produces different effects depending on neutron number: The lowest octupole phonon is rotationally aligned in ¹⁹⁰Hg, is crossed by the aligned two-quasiparticle bands in ¹⁹²Hg, and retains the K=2 octupole vibrational character up to the highest frequency in ¹⁹⁴Hg. The γ vibrations are predicted to be higher in energy and less collective than the octupole vibrations. From a comparison with the experimental dynamic moments of inertia, a new interpretation of the observed excited bands invoking the K=2 octupole vibrations is proposed, which suggests those octupole vibrations may be prevalent in superdeformed Hg nuclei.