= R. M. Cotts
{c}
\b[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.<Pulsed field gradient stimulated echo methods for improved NMR diffusion measurements in heterogeneous systems by R. M. Cotts and others>[Publisher abstract and byline: Journal of Magnetic Resonance83(2),252–266,15June1989]{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.<Pulsed field gradient stimulated echo methods for improved NMR diffusion measurements in heterogeneous systems by R. M. Cotts and others>[Abstract: background-gradient and cross-term effects; tests in bulk glycerol and granular TaH0.73]{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.
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