Precision test of the rotor model from band mixing in Er166

The relative gamma-ray intensities for the gamma-to-ground interband transitions and the gamma band Delta I=2 intraband transitions in Er-166 have been measured with high precision. These intensities have been used to generate interband relative B(E2)'s. The results are presented in a Mikhailov plot and are consistent with a cubic polynomial fit at the 0.60% precision level. The significance of the fit is discussed.