 R. M. Cotts

R. M. Cotts is a credited coauthor of Pulsed field gradient stimulated echo methods for improved NMR diffusion measurements in heterogeneous systems by R. M. Cotts and others, published in 1989. The joint work develops stimulated echo sequences for measuring the translational diffusion of resonant atomic nuclei in materials whose internal magnetic environment is not uniform.^[ref]

Pulsed field gradient NMR relates the attenuation of a stimulated echo to motion. In heterogeneous materials, components with different magnetic susceptibilities can produce background magnetic field gradients, which add attenuation and can bias the inferred diffusion coefficient. The paper describes three modified sequences that reduce these effects; under the stated conditions, bipolar gradient pulses cancel a problematic cross term. Two sequences were tested using proton signals in both a homogeneous liquid and a heterogeneous granular solid.^[ref]

The experimental comparison makes a useful measurement principle concrete: an apparatus can respond to both molecular motion and an unwanted background field variation. A sequence designed to separate these contributions improves the interpretation of a diffusion coefficient measurement.