Local monitoring of proton spin diffusion in static and rotating samples via spy detection

A method is described for investigating local proton “spin diffusion” by means of a ¹³C spin probe. The procedure does not require spectral resolution of proton resonance lines and can be applied in the laboratory frame of reference as well as in the rotating frame. Experimental results are presented for a static single crystal of ferrocene and for a powder sample under magic-angle spinning. The spin-diffusion rate constant is found to be proportional to the spinning speed in the range from 1 to 8 kHz.