Tracking Nuclei on the Move

Phys. Rev. Lett. 97, 175502
(issue of 27 October 2006)
http://focus.aps.org/story/v18/st13

Tracking Nuclei on the Move

Geologists routinely probe subterranean atomic nuclei using nuclear
magnetic resonance (NMR) to learn about the porous structure of rocks
that hold petroleum. Now, in the 27 October PRL, researchers show how
to extend the technique to track the motion of liquid between different
pores. The method could help petroleum engineers extract oil more
efficiently. It could also allow researchers to monitor the motion of
molecules between different microscopic regions in liquid crystals or
biological cells.

To learn about a rock's structure using NMR, researchers first expose a
water-saturated rock to a strong magnetic field. The nuclei of hydrogen
atoms in the water molecules act like tiny bar magnets because of their
internal spins, which tend to line up with the applied field. Then an
oscillating field is briefly added to the initial field to jostle these
aligned spins, causing them to wobble in synch like off-balance tops.
Monitoring the wobbles provides information about the rock structure.

See: http://focus.aps.org/story/v18/st13

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