Sunday, February 19, 2012

Nuclear Spin and Nuclear Magnetic Resonance

The Podkletnov apparatus we're reconstructing in the New Mexico State University Superconductoro Gravity experiment places a superconducting disc in two orthogonal oscillating magnetic fields. Early nuclear magnetic resonance experiments by Bloch and Purcell's groups used a constant magnetic field in combination with an orthogonally oriented RF coil that was driven around 29 MHz, (a frequency in the same range as that used by Podkletnov for the rotation coils). Li and Torr, two of the early researchers of the Podkletnov effect hypothesized that gravitomagnetic fields might be observed as the result of aligned nuclear spins in superconductors.

Figures from Bloch, et. el. NMR setup:

From Rigden, Reviews of Modern Physics, 58, (1986), 433

Rigden, Reviews of Modern Physics, 58, (1986), 433

Figure of orthogonal field coils in Podkletnov apparatus:
From From EE Podkletnov, arxiv, (1997), http://arxiv.org/abs/cond-mat/9701074

I did a little research on nuclear magnetic resonance today and came across a number of good articles on its early development. The first article was a nice review of the development of nuclear magnetic resonance in Reviews of Modern Physics by Rigden. Rigden pointed two articles that detail some of the initial work of Rabi, et. al. to measure nuclear spin. If you've covered the Stern-Gerlach experiment and the different quantum numbers, these are easy to read explanations of the work as it developed.

References:
Li, Torr, Gravitational effects on the magnetic attenuation of superconductors, 46, (1992), 5489
Rigden, Reviews of Modern Physics, 58, (1986), 433
Breit, Rabi, Physical Review, 38, (1931), 2082
Rabi, Physical Review, 49, (1936), 324
Purcell, Pound, Bloembergen, Nuclear Magnetic Resonance Absorption in Hydrogen Gas, Physical Review, 70, (1946), 986
Purcell, Torrey, Pound, Resonance Absorption by Nuclear Magnetic Moments in a Solid, Physical Review, 69, (1946), 37
Bloch, Nuclear Induction, Physical Review, 70, (1946), 460
Bloch, Hansen, Packard, The Nuclear Induction Experiment, Physical Review, 70, (1946), 474
Lindley, NMR–Grandmother of MRI, http://physics.aps.org/story/v18/st18
Pound, From radar to nuclear magnetic resonance, Reviews of Modern Physics, 71, (1999), S54

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