Nuclear Magnetic Resonance in Solids: Thermodynamic Effects of a Pair of rf Pulses

Jeener, Jean; Broekaert, Paul

doi:10.1103/physrev.157.232

Cited by 664 publications

(290 citation statements)

References 20 publications

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“…As suggested by Kemp-Harper and Wimperis 15 this problem can be overcome by using a modified Jeener-Broekaert (JB) pulse sequence. 16 This pulse sequence is described by eqn (1), without the 180°p ulse, with = 45°, and a phase cycling that filters the signal through a second rank zero quantum coherence, T 2,0 . The filtration of unwanted coherences depends on a 90°phase difference between the first 45°and the two previous pulses and not on the exact flip angle.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Multiquantum filters and order in tissues

et al. 2001

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In ordered systems, where the molecular motion is anisotropic, quadrupolar and dipolar interactions are not averaged to zero. In such cases, double quantum (DQ) coherences can be formed. This review deals mainly with the effect of anisotropic motion of water molecules and sodium ions in intact biological tissues on 2 H, 1 H and 23 Na NMR spectroscopy and its application to NMR imaging (MRI).Double quantum filtered (DQF) spectra of water molecules and sodium ions were detected in a variety of ordered biological tissues. In collagen-containing tissues such as ligaments, tendons, cartilage, skin, blood vessels and nerves, the DQ coherences are formed as a result of the interaction with the collagen fibers. In red blood cells and presumably also in nerve axons it stems from the interaction with the cytoskeleton.For 23 Na, an I = 3/2 nucleus, the DQ coherences can also be formed in isotropic media. By a judicial choice of the pulse angle in the DQ pulse sequence only the DQ coherences arising from anisotropic motion are detected. For I = 1 nuclei such as 2 H, DQF spectra can be observed only in ordered structures. Thus, the observation of 2 H DQF spectra is an indication of order. The same is true for pairs of equivalent 1 H nuclei.The dependence of the DQF signal on the creation time of the double quantum coherences is characteristic to each tissue and allows signals to be resolved from different tissues by performing the measurements at different creation times. In this way, the 2 H DQF signals of the different compartments of sciatic nerve were resolved and water diffusion in each compartment was studied independently. In the axon, the diffusion was heavily restricted perpendicular to the axon's long axis, a result from which the axon diameter could be deduced. In blood vessel walls, this characteristic enabled the different layers of the vessel to be viewed and studied under strain.For 2 H, a DQF spectroscopic imaging sequence was used to study the orientation of the collagen fibers in the different zones of articular cartilage and bone plug. The effect of pressure on the fibers and their return to equilibrium was studied as well. In blood vessels, a DQF image was obtained and strain maps of the different layers were calculated.The efficiency of the 1 H DQF imaging technique was demonstrated on a phantom of rat tail where only the four tendons were detected at short creation times. 1 H DQF imaging and spectroscopy followed the healing of a rabbit's ruptured Achilles tendon and the results were far more sensitive to the process than conventional imaging. Finally, the method was implemented on a commercial whole body MRI spectrometer. Images of human wrist and ankle showed a positive contrast for the tendons and ligaments, indicating the potential of the method for clinical imaging.

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Section: Theoretical Backgroundmentioning

confidence: 99%

Multiquantum filters and order in tissues

et al. 2001

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“…Signal arising from Zeeman order during t l is also easily accounted for since it appears immediately after and orthogonal to the final pulse. These are the usual considerations for using the sequence to measure the decay time TID of the dipolar order (205).…”

Section: (Lib 126)mentioning

confidence: 99%

Time-Domain Multiple-Quantum NMR

Weitekamp

1983

Advances in Magnetic and Optical Resonance

194

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The development of time domain multiple quantum nuclear magnetic resonance is reviewed through mid 1982 and some prospects for future development are indicated. Particular attention is given to the problem of obtaining resolved, interpretable, many quantum spectra for anisotropic magnetically isolated systems of coupled spins. New resul~s are presented on a number of topics including the optimization of multiple quantum line intensities, analysis of noise in two dimensional spectroscopy, and the use of order selective excitation for cross polarization between nuclear spin species.

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“…By means of the Jeener-Broekaert (JB) radiofrquency pulse sequence [3] (90 o x −t 12 −45 o y − τ − 45 o y − t), it is possible to transfer the initial equilibrium Zeeman order into the dipolar reservoir and to observe the created dipolar ordered state. During the preparation time t 12 , multi-spin single-quantum coherences develop due to the evolution under the dipolar interaction and the second 45 o y pulse transforms part of the coherences just created into multi-spin order [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Quasiequilibrium states in thermotropic liquid crystals studied by multiple-quantum NMR

Buljubasich

Monti

Acosta

et al. 2009

The Journal of Chemical Physics

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Previous work showed that by means of the Jeener-Broekaert (JB) experiment, two quasiequilibrium states can be selectively prepared in the proton spin system of thermotropic nematic liquid crystals (LC) in a strong magnetic field. The similarity of the experimental results obtained in a variety of LC in a broad Larmor frequency range, with crystal hydrates, supports the assumption that also in LC the two spin reservoirs into which the Zeeman order is transferred, originate in the dipolar energy and that they are associated with a separation in energy scales: a constant of motion related to the stronger dipolar interactions (S), and a second one (W) corresponding to the secular part of the weaker dipolar interactions with regard to the Zeeman and the strong dipolar part. We study the nature of these quasiinvariants in nematic 5CB (4'-pentyl-4-biphenylcarbonitrile) and measure their relaxation times by encoding the multiple quantum coherences of the states following the JB pulse pair on two orthogonal bases, Z and X. The experiments were also performed in powder adamantane at 301 K which is used as a reference compound having only one dipolar quasiinvariant. We show that the evolution of the quantum states during the build up of the quasi-equilibrium state in 5CB prepared under the S condition is similar to the case of powder adamantane and that their quasi-equilibrium density operators have the same tensor structure.In contrast, the second constant of motion, whose explicit operator form is not known, involves a richer composition of multiple quantum coherences on the X basis of even order, in consistency with the truncation inherent in its definition. We exploited the exclusive presence coherences ±4, ±6, ±8, besides 0 and ±2 under the W condition to measure the spin-lattice relaxation time T W accurately, so avoiding experimental difficulties that usually impair dipolar order relaxation measurement such as Zeeman contamination at high fields, and also superposition of the different quasiinvariants. This procedure opens the possibility of measuring the spin-lattice relaxation of a quasiinvariant independent of the Zeeman and S reservoirs, so incorporating a new relaxation parameter useful for studying the complex molecular dynamics in mesophases. In fact, we report the first measurement of T W in a liquid crystal at high magnetic fields. The comparison of the obtained value with the one corresponding to a lower field (16 MHz) points out that the relaxation of the W-order strongly depends on the intensity of the external magnetic field, similarly to the case of the S reservoir, indicating that the relaxation of the W-quasiinvariant is also governed by the cooperative molecular motions.

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Nuclear Magnetic Resonance in Solids: Thermodynamic Effects of a Pair of rf Pulses

Cited by 664 publications

References 20 publications

Multiquantum filters and order in tissues

Multiquantum filters and order in tissues

Time-Domain Multiple-Quantum NMR

Quasiequilibrium states in thermotropic liquid crystals studied by multiple-quantum NMR

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