Fast-Passage Effects in the Nuclear Magnetic Resonance ofFe57in Pure Iron Metal

The nuclear magnetic resonance of ${\mathrm{Fe}}^{57}$ in pure iron metal has been examined. The results of the experiments have been analyzed in terms of Portis' theories of saturation and fast passage in inhomogeneously broadened spin systems. The principal results are the following: The value of the enhancement factor for iron $\eta =2000\mathrm{}$ independent of temperature, the values of the spin-lattice relaxation time $T_1=0.25\mathrm{}$ msec at $T=295\mathrm{}°$K, and $T_1=1.3\mathrm{}$ msec at $T=77\mathrm{}°$K, and the fact that the dispersion mode of the nuclear susceptibility is coupled out into the power absorbed more strongly than the absorption mode (in the limit of zero saturation). In addition it is found that the distribution of hyperfine fields is plotted directly due to fast-passage effects. This is identified as a fast-passage effect by the observation that the signal amplitude does not increase linearly with the modulation amplitude and by other tests.