Macroscopic and Microscopic Fields in High-Resolution Liquid NMR

Vlassenbroek, Alain; Jeener, Jean; Broekaert, Paul

doi:10.1006/jmra.1996.0032

Cited by 56 publications

(60 citation statements)

References 7 publications

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“…Fortunately, in the XY MAXCRAZED experiment (ŝ =x,ŝ =ŷ) the value of for both of these components is the same (−1/2) so Eqs. (20) and (21) hold. We then have z = ⊥ = −1/2, and the homomolecular coupling is 1.5 times greater than the homomolecular, just as in CRAZED.…”

Section: Revised Framework For Dipolar Effectsmentioning

confidence: 94%

“…(4) (for example, the field from a spherical sample is zero inside the sphere, and equivalent to the field from a point dipole outside the sphere), 20 but in general the dipolar field predicted by the integral in Eq. (4) is nonlocal with components in all directions.…”

Section: Review Of Conventional Dipolar Field Treatmentsmentioning

confidence: 99%

“…For the matched-gradient pair sequences in Figures 1(a), 1(b), and 4, the first pulse flip angle is chosen to be extremely small, so that almost all of the magnetization remains along the z-axis and produces no dipolar field. Equation (20) simplifies to…”

Section: Revised Framework For Dipolar Effectsmentioning

confidence: 99%

“…(20) and (21). At the beginning of the interval d 2 , the transverse magnetization is modulated with two spatial frequencies,…”

Section: Revised Framework For Dipolar Effectsmentioning

confidence: 99%

“…(20) and (21) invalid. Fortunately, in the XY MAXCRAZED experiment (ŝ =x,ŝ =ŷ) the value of for both of these components is the same (−1/2) so Eqs.…”

Section: Revised Framework For Dipolar Effectsmentioning

confidence: 99%

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Revisiting the mean-field picture of dipolar effects in solution NMR

Chen

Branca

Warren

2012

The Journal of Chemical Physics

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For more than three decades, the classical or mean-field picture describing the distant dipolar field has been almost always simplified to an effective field proportional to the local longitudinal magnetization, differing only by a scale factor of 1.5 for homomolecular (identical resonance frequency) and heteromolecular interactions. We re-examine the underlying assumptions, and show both theoretically and experimentally that the mathematical framework needs to be modified for modern applications such as imaging. We demonstrate new pulse sequences which produce unexpected effects; for example, modulating an arbitrarily small fraction of the magnetization can substantially alter the frequency evolution. Thus, matched gradient pulse pairs (a seemingly innocuous module in thousands of existing pulse sequences) can alter the time evolution in highly unexpected ways, particularly with small flip angle pulses such as those used in hyperpolarized experiments. We also show that specific gradient pulse combinations can retain only dipolar interactions between unlike spins, and the dipolar field can generate a secular Hamiltonian proportional to I x .

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Section: Revised Framework For Dipolar Effectsmentioning

confidence: 94%

Section: Review Of Conventional Dipolar Field Treatmentsmentioning

confidence: 99%

Section: Revised Framework For Dipolar Effectsmentioning

confidence: 99%

“…(20) and (21). At the beginning of the interval d 2 , the transverse magnetization is modulated with two spatial frequencies,…”

Section: Revised Framework For Dipolar Effectsmentioning

confidence: 99%

“…(20) and (21) invalid. Fortunately, in the XY MAXCRAZED experiment (ŝ =x,ŝ =ŷ) the value of for both of these components is the same (−1/2) so Eqs.…”

Section: Revised Framework For Dipolar Effectsmentioning

confidence: 99%

See 3 more Smart Citations

Revisiting the mean-field picture of dipolar effects in solution NMR

Chen

Branca

Warren

2012

The Journal of Chemical Physics

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Understanding radiation damping in a simple way

Mao

1997

Concepts Magn. Reson.

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A simple picture is provided about various radiation‐damping effects in NMR, as follows: free‐induction decay can grow before it decays; signal intensity shows a sawtooth profile as a function of the pulse flip angle; a twisted signal phase can appear when the pulse flip angle is greater than 90°; spin ‐ lattice relaxation times cannot be measured by the routine inversion ‐ recovery method, and spin ‐ spin relaxation times cannot be estimated by the simple spin ‐ echo method; a z gradient pulse sometimes fails to suppress radiation damping; and in two‐dimensional experiments there can be strong harmonic peaks in the indirectly detected dimension. © 1997 John Wiley & Sons, Inc. Concepts Magn Reson 9: 173–187, 1997

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