Eur. Phys. J. A (2010) 45: 81-90
https://doi.org/10.1140/epja/i2010-10982-2

Regular Article - Theoretical Physics

The IBM description of triaxial nuclei

Laboratoire de Physique Subatomique et de Cosmologie, IN2P3-CNRS/Universite Joseph Fourier, F-38026, Grenoble Cedex, France

^* e-mail: thiamova@lpsc.in2p3.fr

Received: 13 February 2010
Revised: 30 April 2010
Accepted: 4 May 2010
Published online: 23 June 2010

Abstract

Recently, interacting boson model (IBM) calculations, in the O(6) basis up to the seniority quantum number v _max= 40 , were made possible thanks to the availability of the SO(5) Clebsch-Gordan (CG) coefficients, computed in floating-point arithmetic (T.A. Welsh, unpublished (2008)). In this paper we have made use of these CG coefficients to extend the IBM to situations where triaxial deformation is present. Such a description has been considered in the algebraic collective model (ACM) which is an algebraic version of the Bohr model. To describe triaxiality in the ACM a term proportional to cos²3 must be included in the Hamiltonian. We show that, in the IBM, this can be achieved by including a term quadratic in ( ⊗ ⊗ )₀, which is an IBM image of the term cos²3 . Quadrupole shape invariants are used to investigate the and rigidity of the states obtained with such a Hamiltonian and a comparison with the rigid asymmetric rotor model is presented. The staggering of -band level energies, obtained in the present approach, is analyzed and compared to the ones predicted by the geometrical models and by the IBM. A comparison between the experimental and calculated staggerings in ¹⁹⁰Os and ¹⁹²Os is shown.