Abstract
An algebraic model with three-body boson interactions is proposed to incorporate the different quadru-pole modes in nuclear collectivity.It is shown that the recently observed anomalous collective structure character-ized by B4/2=B(E2;4 1 → 2 1)/B(E2;2 1 → 0 1)＜1.0 and R4/2=E(4 1)/E(2 1)≥2.0,which cannot yet be explained by any other microscopic nuclear models,naturally emerges in the present model due to the inclusion of triaxial ro-tor modes.This description is further extended to describe odd-A nuclei by including the coupling to the Fermion de-gree of freedom.This allows us to give a unified explanation of the anomalous B(E2)strengths in both even-even and even-odd systems,which indicate different behaviors.As examples,the model is applied to describe the spectro-scopy and E2 transition properties of 168,169,170,171 Os.Allrecent measurements of these isotopes can be well repro-duced on the same footing,which suggests that the anomalous collectivity persists even in odd-A systems.
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