Indirect detection of NMR via geometry-dependent dipolar fields, revisited

Journal of Magnetic Resonance

Volumn 186, Issue 2, 2007, Pages 330-336

  Dong, Wei ^a   Meriles, C A ^a  

^a CITY COLLEGE OF NEW YORK   (United States)

Author keywords

Dipolar field microscopy; Distant dipolar fields

Indexed keywords

APPROXIMATION THEORY; MAGNETIC RELAXATION; MAGNETIC SENSORS; MAGNETIZATION; SIGNAL PROCESSING;

DIPOLAR FIELD MICROSCOPY; DIPOLAR INTERACTIONS; DISTANT DIPOLAR FIELDS;

NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY;

OIL; WATER;

ARTICLE; CHEMISTRY; FOURIER ANALYSIS; MAGNETISM; METHODOLOGY; NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY; TIME;

FOURIER ANALYSIS; MAGNETIC RESONANCE SPECTROSCOPY; MAGNETICS; OILS; TIME FACTORS; WATER;

EID: 34249942559     PISSN: 10907807     EISSN: 10960856     Source Type: Journal    
DOI: 10.1016/j.jmr.2007.02.012     Document Type: Article

References (22)

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14. Because the sample magnetic field is to be calculated only on the region occupied by the sensor, it is enough to divide the sample volume into sufficiently small compartments dV with magnetic moment dμ = MdV, with M the magnetization of the sample (assumed homogeneous). The magnetic field at a given point on the sensor is obtained by co-adding the contributions to the field at a given point from all elementary dipoles dμ. See, for example,. Jackson J.D. Classical Electrodynamics. third ed. (1999), Wiley, New York Chapter 5
15. Note that in the absence of dipolar fields on the sensor, this procedure exactly cancels the observed signal. See Ref. [13] for further details.
16. This procedure also eliminates contributions due to homonuclear dipolar fields on the sensor itself. It is worth indicating, however, that homonuclear contributions are expected to be comparatively weak anyhow. This is because the longitudinal component of the sensor magnetization remains small during most of the 'decoding' period; effects due to corotating components can also be neglected given the much stronger field inhomogeneity in our setup (the line broadening of both sensor and sample resonances was ∼150 Hz).
17. - 1, this simpler representation is approximately correct as a simple numerical calculation demonstrates for the system under consideration.
18. In our setup, this was observed after 15 inversions.
19. spl will be the most common scenario.
20. Inhomogeneity of the sample dipolar field over the sensor contributes to further reduce the amplitude of the sensor signal. In the absence of relaxation and for a cylindrical sensor of height equal to its radius, the maximum encoded signal corresponds to approximately 30% of that induced by the sensor full magnetization.
21. Meriles C.A. Optical detection of nuclear magnetic resonance at the sub-micron scale. J. Magn. Reson. 176 (2005) 207
22. Note that in this case, an 'encoding' period is necessary to select the part of the sample to be probed. See Refs. [13] and [21] for further details.