Precession mode on high-K configurations: Non-collective axially-symmetric limit of wobbling motion

The precession mode, the rotational excitation built on the high-K isomeric state, in comparison with the recently identified wobbling mode has been studied. The random-phase-approximation (RPA) formalism, which has been developed for the nuclear wobbling motion, is invoked and the precession phonon is obtained by the non-collective axially symmetric limit of the formalism. The excitation energies and the electromagnetic properties of the precession bands in ¹⁷⁸W are calculated, and it is found that the results of RPA calculations well correspond to those of the rotor model; the correspondence can be understood by an adiabatic approximation to the RPA phonon. As a by-product, it is also found that the problem of too small out-of-band B(E2) in our previous RPA wobbling calculations can be solved by a suitable choice of the triaxial deformation which corresponds to the one used in the rotor model.