Use of the Stimulated Echo in NMR Diffusion Studies

The stimulated echo in a three‐rf‐pulse experiment is shown to be useful in extending the range of measurement of diffusion coefficients to more viscous substances or the measurement of barrier separations to wider spacings in systems where the diffusing substance has $T_1{\mathrm{\hspace{0.17em}>\hspace{0.17em}T}}_2$ . The spin‐echo attenuation due to self‐diffusion is derived for the general case of a time‐dependent field gradient, and the result is found experimentally to be correct for the special case of a field gradient applied in two equal, square pulses.