Single-Passage Resonance Studies byβEmission and the Measurement of Spin-Lattice Relaxation Times forFe60Co

$\beta$-particle measurements of the signal produced during single- and multiple-passage nuclear magnetic resonance of oriented ${}_{}{}^{60}{}_{}{}^{}\mathrm{Co}$ nuclei in single crystals of iron are reported. Comparison of the signals from ${\beta }^{-}$ and $\gamma$ radiations shows that after single passages the changes in the orientation parameters are describable in terms of a rotation through a well-defined angle. This constitutes a known set of initial conditions for the subsequent relaxation back to equilibrium so that accurate values of the spin-lattice relaxation time $T_1$ can be obtained. A nonresonant method of measuring $T_1$ accurately is also described and is shown to give results in agreement with the single-passage technique. We obtain a value $K=1.75\mathrm{}\pm 0.15$ sec K for ${\mathrm{Fe}}^{60}\mathrm{Co}$. This differs from values previously reported from experiments in which the initial conditions were not well known. Comparison of the ${\beta }^{-}$ and $\gamma$ signals after multiple passages show, as expected, that the changes in the orientation parameters are not then describable in terms of a single angle of rotation.