Precision measurement of theg-factor of the 2+ ?-vibrational state of160Dy and test of theF-spin purity

Abstract

The rotations of the 392-966 keV and the 299–966 keV directional correlations of160Dy in the static hyperfine field of DyTb have been measured with high precision. A neutron activated Tb single crystal was used which was magnetized to saturation at 4.2 K by an external magnetic field of 4.5 T applied in the direction of theb-axis. The agreement of both rotations proves that the relaxation of the 4f-shell after theβ-decay takes less than 10 ps. A quantum mechanical calculation within the magnon model gave a relaxation time of the order of 1 ps. Theg-factor of the 2+γ-vibrational state was derived as $$g(2_\gamma ^ + ) = + 0.317(12)$$ and combining our results with Mossbauer data [24] on the magnetic splitting of the 2rot+ state in the same environment we obtain $$g(2_\gamma ^ + )/g(2_{rot}^ + ) = 0.82(3).$$ . The results are discussed within the Bohr-Mottelson model and finally within the IBM-2 model in terms ofF-spin purity.