The sign change of the M1 matrix element in Δ K = 2 transitions in 166Er

High precision measurements of multipole mixing ratios of nine M1 + E2 transitions between the γ-band and the ground state band in 166Er show variations in both magnitude and sign of δ. The dynamic deformation model provides a satisfactory basis on which to examine these variations and predicts the measured sign in every case and also obtains good agreement with the magnitudes. The model results show that the sign of δ is determined by the sign of the M1 matrix element. Calculated B(E2) values are in good agreement with the available experimental results. (author)