Anharmonic double-phonon excitations in the interacting boson model

Abstract

Double−γ vibrations in deformed nuclei are analyzed in the context of the interacting boson model. A simple extension of the original version of the model towards higher-order interactions is required to explain the observed anharmonicities of nuclear vibrations. The influence of three- and four-body interactions on the moments of inertia of ground and γ bands, and on the relative position of single−γ and double−γ bands is studied in detail. As an example of a realistic calculation, spectra and transitions of the highly γ−anharmonic nuclei 164Dy, 166Er, and 168Er are interpreted in this approach.