Triaxial nuclear shapes of even–even ruthenium isotopic chain in the O(6) dynamical symmetry of interacting boson model with the three-body quadrupole interaction

Abstract

Even–even nuclei in the $$ A\sim100 $$ mass region are investigated within the framework of the sd-interacting boson model (sdIBM1) with three-body O(6) symmetric quadrupole operator $$ \left[ {QQQ} \right]^{\left( 0 \right)} $$ for generating states with triaxial deformation. The rigid triaxial asymmetric rotor model of collective rotation is used to extract the asymmetry parameter $$ \gamma $$ from both the energy ratio of the second $$ 2_{2}^{ + } $$ state to the first $$ 2_{1}^{ + } $$ state and the reduced E2 transition probabilities from $$ 2_{1,2}^{ + } $$ states to the ground state. Using the method of the intrinsic coherent states, the classical limit of potential energy surfaces which represents the expectation value of the total Hamiltonian is obtained. The critical points of the phase transition are investigated. The triaxiality is analyzed for even–even ruthenium (Ru) isotopic chain as an example of illustrating the effect of the three-body quadrupole operator. By using computer simulated search program, a fitting procedure is performed to get the best parameters of the IBM Hamiltonian for each nucleus in order to obtain a minimum root mean square deviation between the calculated and the experimental some low-lying energy levels and B(E2) transition rates.