scholarly journals Environment-induced corrections to the spin Hamiltonian as dynamic frequency shifts in nuclear magnetic resonance

2000 ◽  
Vol 113 (17) ◽  
pp. 7131-7139 ◽  
Author(s):  
G. Karthik ◽  
Anil Kumar
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Spin Hamiltonian ◽  
Frequency Shifts ◽  
Dynamic Frequency ◽  
Nuclear Magnetic

Nuclear magnetic resonance reorientational correlation functions: the odd-valued spectral components

1979 ◽  
Vol 57 (17) ◽  
pp. 2329-2332 ◽  
Author(s):  
Catherine Elisabeth Marie Fouques ◽  
Lawrence G. Werbelow
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Cross Correlation ◽  
Modulation Frequency ◽  
Nuclear Magnetic Resonance Experiment ◽  
Critical Assessment ◽  
Spectral Components ◽  
Angular Correlation Function ◽  
Dynamic Frequency ◽  
Nuclear Magnetic

Practical consequences attributable to nonvanishing imaginary spectral components of the second rank spherical harmonic angular correlation function are described in detail. This analysis presumes the absence of macroscopic spatial anisotropies. Modulation frequency, anisotropy, and cross correlation of interaction between a nuclear spin and the extranuclear environment are considered. These findings permit a critical assessment of the second-order ultrafine dynamic frequency shift in the nuclear magnetic resonance experiment.

Nuclear magnetic resonance and magnetic structure of antiferromagnetic Mn2P2O7

1970 ◽  
Vol 48 (5) ◽  
pp. 521-530 ◽  
Author(s):  
Sung Ho Choh ◽  
C. V. Stager
Keyword(s):  
Experimental Data ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
External Field ◽  
Hamiltonian Formalism ◽  
Single Crystal Sample ◽  
Spin Hamiltonian ◽  
Crystal Sample ◽  
Made In ◽  
Nuclear Magnetic

The nuclear magnetic resonance of 31P in antiferromagnetic Mn2P2O7 has been investigated at constant r.f. frequencies with the external field smaller than the spin-flop field. Resonance measurements were made in a single crystal sample at liquid helium temperatures. Experimental data, including the angular dependence, the external field dependence, and the temperature dependence of the resonances, are satisfactorily explained by the spin Hamiltonian formalism for NMR in antiferromagnets, proposed by the authors. NMR results confirm the spin direction obtained from susceptibility measurements, and establish the magnetic space group as C2c2.

An emerging technology: Nuclear magnetic resonance microscopy

1988 ◽  
Vol 46 ◽  
pp. 1000-1001
Author(s):  
M.J. Hennessy ◽  
E. Kwok
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Basic Research ◽  
Local Environment ◽  
Magnetic Resonance Images ◽  
Nmr Microscopy ◽  
Mri Scans ◽  
Temperature Relaxation ◽  
Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

Nuclear magnetic resonance microscopy

1989 ◽  
Vol 47 ◽  
pp. 828-829
Author(s):  
Paul C. Lauterbur
Keyword(s):  
Magnetic Field ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Fields ◽  
Signal To Noise ◽  
Field Gradients ◽  
Useful Signal ◽  
Magnetic Field Gradients ◽  
Observation Times ◽  
Nuclear Magnetic

Nuclear magnetic resonance imaging can reach microscopic resolution, as was noted many years ago, but the first serious attempt to explore the limits of the possibilities was made by Hedges. Resolution is ultimately limited under most circumstances by the signal-to-noise ratio, which is greater for small radio receiver coils, high magnetic fields and long observation times. The strongest signals in biological applications are obtained from water protons; for the usual magnetic fields used in NMR experiments (2-14 tesla), receiver coils of one to several millimeters in diameter, and observation times of a number of minutes, the volume resolution will be limited to a few hundred or thousand cubic micrometers. The proportions of voxels may be freely chosen within wide limits by varying the details of the imaging procedure. For isotropic resolution, therefore, objects of the order of (10μm) may be distinguished.Because the spatial coordinates are encoded by magnetic field gradients, the NMR resonance frequency differences, which determine the potential spatial resolution, may be made very large. As noted above, however, the corresponding volumes may become too small to give useful signal-to-noise ratios. In the presence of magnetic field gradients there will also be a loss of signal strength and resolution because molecular diffusion causes the coherence of the NMR signal to decay more rapidly than it otherwise would. This phenomenon is especially important in microscopic imaging.

Sign in / Sign up

Export Citation Format

Share Document