Pulsed-Microwave Studies of Conduction-Electron Spin Resonance in Lithium and Sodium

Free-induction and echo signals from Li and Na conduction-electron spins have been studied using a pulsed-microwave spectrometer. The resonance lines were found to be homogeneous under all experimental conditions, and echoes could only be obtained by degrading the external field homogeneity. Measurements of the free-induction decay were in agreement with the decay calculated for a Dysonian line shape. The weakness of the observed echoes is attributed to the diffusion of spins in the metal, which tends to average out inhomogeneities in the local steady fields whether they originate from microscopic interactions or from external field gradients. The measurements were made with a coherent, homodyne, $X$-band apparatus, a description of which is given.