Spin and magnetic moment of the 1.094-MeV state in 168Er

The time-differential directional-correlation function of the 448 - 198-keV γ-γ cascade has been measured and the half-life of the 1.094-MeV state in ¹⁶⁸Er is found to be 107.3±2.2 nsec. The time-differential behavior of A₂₂(t) shows a possible time-dependent interaction with a decay constant λ₂=(1.0±0.5)×10⁷ nsec⁻¹. Extrapolation of A₂₂(t) to zero time-delay gives A₂₂(0)=0.007±0.004, which is compatible with spin 4 for the 1.094-MeV state and multipolarity M1+<8%E2 for the 448-keV transition. The g-factor of the 1.094-MeV state has been measured, by use of the constant-angle-differential-delay method, and is found to be g=+0.45±0.02. The time-dependent perturbation is interpreted in terms of rapidly fluctuating $4f$ electron magnetic hyperfine fields with a time-averaged value of 0.9 MG in Er³⁺ at room temperature.[NUCLEAR MOMENTS ¹⁶⁸Er level; measured γγ coin., deduced J, T_1/2, γ mixing. Measured γγ(θ,H), D. D. C. A. method, deduced g, Er³⁺ hyperfine field.]