E2 SELECTION-RULES OF GAMMA-RIGID AND GAMMA-UNSTABLE ROTORS

It has been known that the E2 selection rules are similar between the Davydov-Filippov rigid triaxial rotor model with gamma = 30 degrees an d the O(6) limit of the interacting boson model (IBM). Using the O(6) limit of IBM, we investigate the relationship of the wavefunctions of O(6) and those of the Davydov-Filippov model. We introduce an intrinsi c state with a fixed gamma-value and construct its intrinsic excitatio n. It was shown by Ginocchio and Kirson that the O(6) wavefunctions ca n be expressed using the intrinsic state by the integration with respe ct to the gamma-value. A formula is given which expresses the O(6) wav efunctions as a superposition of the gamma-fixed intrinsic state and i ts intrinsic excitation. A discrete symmetry of these intrinsic excita tions has been found, and by using this symmetry, we analyze the close connection between the E2 selection rules of the Davydov-Filippov rot or model and the O(6) limit of IBM.