Tilted precession and wobbling in triaxial nuclei

Abstract

The rotation of a triaxial nucleus can be represented (in a semiclassical description) as a precession of the total angular momentum around a certain axis and at a given tilt, producing tilted precession (TiP) bands. Such bands are described by rotational models and can in principle be approximated with wobbling. We studied for which TiP bands such an approximation is justified. It was found that TiP bands become approximately similar to wobbling bands at high spins for both zero-seniority bands in even-even nuclei, and one-quasiparticle bands with longitudinal coupling of the angular momenta in odd-mass nuclei. Contrary to that, the precession for transverse coupling of the angular momenta in one-quasiparticle configurations giving rise to TiP bands cannot be approximated with wobbling either at low or at high spins. This suggests that the interpretation of a band in terms of transverse wobbling cannot be justified only by particle-rotor-type model, as this model implies a different, TiP, nature. Contrary to TiP bands, the transverse wobbling bands exhibit quantized excitation energies and transition probabilities which is typical for bands involving phonon excitations.