John E. Tanner
= John E. Tanner
{c}
{title2=1930-2023}
= J. E. Tanner
{c}
{synonym}
\b[John E. Tanner] was a <physical chemistry> researcher whose work with <Edward O. Stejskal> established <pulsed field gradient NMR> as a method for measuring <self-diffusion>. He studied <physical chemistry> at Oberlin, Indiana and Wisconsin, and later worked at Idaho National Laboratory. His early <NMR> work received renewed recognition with an honorary fellowship in 2016.<John Tanner obituary by Michigan Cremation and Funeral Care>[Life dates, education, Idaho career and 2016 recognition]{ref}
\Image[https://cdn.tukioswebsites.com/f174b7be-078a-4f72-9019-f76ff591e46b/lg]
{title=John E. Tanner, from the profile portrait accompanying his family memorial}
{height=300}
The appeal of <pulsed field gradient NMR> was practical as well as theoretical: strong <magnetic field gradients> could encode motion without remaining strong during excitation or detection. In a 2017 interview with <Derek Jones (magnetic resonance researcher)>, Tanner recalled choosing Stejskal's laboratory because it had a magnet and because he wanted to measure slow <diffusion>. He also described rebuilding the probe to deal with <eddy currents> generated by switching the <magnetic field gradients>.<John Tanner, the return to Germelshausen, and the work that nearly never happened by Derek Jones>[pp.4 and7: choice of doctoral work, gradient switching and probe redesign]{ref}
Tanner made <restricted diffusion> experimentally concrete. He described assembling 99 layers of <mica> with <aluminium> foil spacers, carefully removing wrinkles and burrs to obtain regular gaps. Such a controlled geometry lets an echo probe displacement between known barriers, rather than treating every loss of <NMR> <signal> as free <diffusion> with a smaller <diffusion coefficient>.<John Tanner, the return to Germelshausen, and the work that nearly never happened by Derek Jones>[p.6: mica-stack construction and interpretation of restricted geometry]{ref}
His 1970 work used a <stimulated echo> to extend the observation interval when <spin-lattice relaxation> is slower than <transverse relaxation>. The interval can store the relevant pattern as longitudinal <magnetization>, rather than keeping it transverse throughout.<Use of the Stimulated Echo in NMR Diffusion Studies by J. E. Tanner>[Original abstract: three-pulse method, T1 greater than T2 and experimental square-gradient test]{ref} For an illustrative ideal comparison, take $T_1=1\,\mathrm s$, $T_2=0.1\,\mathrm s$ and storage time $T=0.5\,\mathrm s$. The storage-dependent <nuclear spin relaxation> factors are $e^{-T/T_1}\simeq0.607$ and $e^{-T/T_2}\simeq0.00674$. Even allowing the ideal three-pulse pathway's initial factor of $1/2$, the former factor is about \b[45 times larger]. This compares only that storage contribution: pulse losses, the other transverse intervals and <diffusion> attenuation still matter.<John Tanner, the return to Germelshausen, and the work that nearly never happened by Derek Jones>[p.6: Tanner's explanation of the half-signal cost versus longer T1 storage]{ref}