Pulsed-Beam Measurement of the Gyromagnetic Ratio of the First Excited Rotational States in Ytterbium 172, 174, and 176

The gyromagnetic ratio $g$ of the first excited rotational states in ytterbium 172, 174, and 176 has been measured using the pulsed-beam technique. The precession of the Coulomb-excited nuclei in an external magnetic field has been detected by observing the angular distribution of the de-excitation gamma radiation as a function of time. The measured $g$ factors and mean lives ($\tau$) are: $g=0.279\mathrm{}\pm 0.014$, $\tau =2.46\mathrm{}\pm 0.07$ nsec for ${\mathrm{Yb}}^{172}$; $g=0.247\mathrm{}\pm 0.013$, $\tau =2.59\mathrm{}\pm 0.07$ nsec for ${\mathrm{Yb}}^{174}$; $g=0.299\mathrm{}\pm 0.015$, $\tau =2.54\mathrm{}\pm 0.07$ nsec for ${\mathrm{Yb}}^{176}$. The timing techniques which make possible an evaluation of the effect of target perturbations on the measurement are discussed. These measurements were made in ytterbium-metal targets where the magnetic field at the nucleus is essentially the applied external magnetic field.