Effective γ deformation nearA=130 in the interacting boson model

‘‘Effective’’ γ-deformation parameters are derived for even-even Xe, Ba, and Ce nuclei from the matrix elements of (Q×Q${)}_{00}$ and (Q×Q×Q${)}_{00}$. Interacting boson model calculations are performed with the quadrupole operator Q determined from the E2 branching ratios of the $2_2^{+}$ decay and compared to results obtained with the rigid triaxial rotor model. © 1996 The American Physical Society.