First Direct Measurement of the Spin Diffusion Rate in a Homogenous Solid

The first direct measurement of the rate of spin diffusion through a homogeneous sample is reported. The measurement was performed as an incoherent scattering experiment via a combination of pulsed gradient spin echo methods with multiple pulse, pulsed gradient spatial encoding. The measurement records the destruction of a spin magnetization grating by the random translation of spin magnetization associated with the flip-flop term of the homonuclear dipole-dipole interaction. For single crystal CaF₂, the measured parallel components of the spin diffusion rates are 7.1×10^-12cm²/s along the [001] direction and 5.3×10^-12cm²/s along the [111] direction, in good agreement with theoretical predictions.