Dramatic transition between electric and magnetic rotations in ¹⁰⁶Ag

The lifetimes for the states of magnetic dipole band in ¹⁰⁶Ag have been measured using the Doppler-shift attenuation method via the reaction of ¹⁰⁰Mo(¹¹B, 5n)¹⁰⁶Ag at a beam energy of 60 MeV. The reduced transition strengths of the magnetic dipole band, the B(M1)/B(E2) ratios together with the signature of the level energy as a function of angular momentum for the positive parity states of ¹⁰⁶Ag show that a drastic change of excitation mode, that is, from electric rotation to magnetic rotation, occurs within one unit of spin at around I ^π = 12⁺. Theoretical calculations based on the triaxial projected shell model consistently reproduce the experimental data and provide an explanation on the nature of observed phenomena such that the dynamical drift of the rotational axis suddenly from the principal axis to the tilted one, along the positive parity bands of ¹⁰⁶Ag.