Abstract
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.
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