Zeeman-Incremented Multiple-Quantum NMR

doi:10.1006/jmra.1993.1171

Journal of Magnetic Resonance, Series A

Volume 103, Issue 3, July 1993, Pages 307-312

https://doi.org/10.1006/jmra.1993.1171 Get rights and content

Abstract

A new method for performing multiple-quantum NMR experiments is described. Instead of incrementing the evolution period t₁ in the conventional manner, t₁ is kept fixed while the magnetic field is increased, successively. The method is illustrated using ¹⁹F spins in dipolar coupled 2,2-difluorotetrachloroethane, 1,1,1 -trichlorotrifluoroethane, and hexafluorobenzene, oriented in a nematic liquid crystal. It is demonstrated that Zeeman-incremented multiple-quantum NMR experiments give rise to simplified spectra in the multiple-quantum t₁ domain, free from T₂ decay. For example, in the case of hexafluorobenzene, just seven equally spaced peaks are observed, corresponding to Δm = ± 0, 1, . . . , 6.

References (0)

Cited by (4)

Electron-Zeeman resolved electron paramagnetic resonance spectroscopy
2001, Journal of Magnetic Resonance
Electron-Zeeman (EZ) resolved electron paramagnetic resonance (EPR) spectroscopy is introduced. In this two-dimensional pulse EPR technique a sinusoidal external field ΔB₀(t) of variable amplitude is applied during the pulse sequence, resulting in a field-swept EPR spectrum that is spread into a second dimension, representing the g values of the paramagnetic species. The method can be used to improve the resolution of polycrystalline and single-crystal EPR spectra. For polycrystalline systems, simplified EPR spectra are obtained for fixed g values. For axial symmetry, these spectra allow direct access to coupling constants, also at orientations that differ from the principal axes orientations. Furthermore, overlapping resonances can be disentangled, extra-absorption peaks identified and unresolved hyperfine splittings observed. The sum projection onto the g-value axis corresponds in a g-value spectrum, which is free of hyperfine interactions. A detailed theoretical description of the EZ-EPR experiment is given. Several model calculations for systems with different symmetry of the magnetic interaction tensors are presented, and the versatility of EZ-EPR is demonstrated for different paramagnetic systems with g anisotropy.
Elimination of Longitudinal Multiple-Quantum Artifacts in 2D COSY Spectra
1994, Journal of Magnetic Resonance, Series A
A detailed analysis of phase-cycling procedures in COSY 2D NMR experiments is described. It is shown that a phase-cycling scheme, originally proposed by Rinaldi and Iverson (J. Magn. Reson. 92, 528, 1991) can be used to eliminate all longitudinal MQ artifacts of even order Δm = 0, ±2, ±4, etc., exactly. In addition, it is demonstrated that in rotation-sensitive experiments, designed to produce an N-type Δm = −1 peak, the odd-order multiple-quantum artifact Δm = +3 appears as a P-type peak. Thus rotation-sensitive COSY experiments can be used to discriminate against Δm = 0, ±2, ±3, and ±4 MQ artifacts. The theoretical results are confirmed experimentally, using a nominally isolated spin- $12$ ensemble, which can be made to generate MQ artifacts as high as Δm = ±5.
Determination of relaxation times for zero-order multipolar states using Zeeman-Incremented NMR techniques
1993, Journal of Magnetic Resonance - Series A
The design of biplanar, shielded, minimum energy, or minimum power pulsed B<inf>0</inf> coils
1995, Magma: Magnetic Resonance Materials in Physics, Biology, and Medicine

View full text

Regular ArticleZeeman-Incremented Multiple-Quantum NMR

Abstract

Regular Article
Zeeman-Incremented Multiple-Quantum NMR