Rotational constants of multi-phonon bands in an effective theory for deformed nuclei

Abstract

We consider deformed nuclei within an effective theory that exploits the small ratio between rotational and vibrational excitations. For even-even nuclei, the effective theory predicts small changes in the rotational constants of bands built on multi-phonon excitations that are linear in the number of excited phonons. In 166Er and 168Er, this explains the main variations of the rotational constants of the two-phonon gamma vibrational bands. In 232Th, the effective theory correctly explains the trend that the rotational constants decrease with increasing spin of the band head. We also study the effective theory for deformed odd nuclei. Here, time-odd terms enter the Lagrangian and generate effective magnetic forces that yield the high level densities observed in such nuclei.