Noise current measurements and signal‐to‐noise improvement in low‐temperature, low‐frequency nuclear‐magnetic‐resonance experiments

1984 ◽  
Vol 55 (4) ◽  
pp. 521-526 ◽  
Author(s):  
J. Lepaisant ◽  
D. Bloyet ◽  
E. Varoquaux
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Temperature ◽  
Low Frequency ◽  
Signal To Noise ◽  
Noise Current ◽  
Nuclear Magnetic

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.

Nuclear Magnetic Resonance Studies of δ-Stabilized Plutonium

2003 ◽  
Vol 802 ◽  
Author(s):  
N. J. Curro ◽  
L. Morales
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Frequency ◽  
Lattice Relaxation ◽  
Spin Fluctuations ◽  
Spin Lattice Relaxation ◽  
Cubic Symmetry ◽  
Magnetic Resonance Studies ◽  
Local Distortions ◽  
Nuclear Magnetic

Nuclear Magnetic Resonance studies of Ga stabilized δ-Pu reveal detailed information about the local distortions surrounding the Ga impurities as well as provides information about the local spin fluctuations experienced by the Ga nuclei. The Ga NMR spectrum is inhomogeneously broadened by a distribution of local electric field gradients (EFGs), which indicates that the Ga experiences local distortions from cubic symmetry. The Knight shift and spin lattice relaxation rate indicate that the Ga is dominantly coupled to the Fermi surface via core polarization, and is inconsistent with magnetic order or low frequency spin correlations.

A 19F nuclear magnetic resonance and Raman spectroscopic investigation of the reaction of iodine oxide pentafluoride with the Lewis acids, antimony and arsenic pentafluoride

1978 ◽  
Vol 56 (17) ◽  
pp. 2253-2258 ◽  
Author(s):  
Morley Brownstein ◽  
Ronald J Gillespie ◽  
John P. Krasznai
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Raman Spectroscopy ◽  
Magnetic Resonance ◽  
Low Temperature ◽  
Oxygen Atom ◽  
Spectroscopic Investigation ◽  
Lewis Acids ◽  
Raman Spectroscopic ◽  
Nuclear Magnetic

The reactions of IOF5 with SbF5 and with AsF5 have been investigated at low temperature by 19F nmr and Raman spectroscopy. It was found that SbF5 forms labile 1:1 and 2:1 complexes whereas AsF5 forms only a 1:1 complex. The IOF5 is bound through its oxygen atom to the Lewis acids AsF5, SbF5, or (SbF5)2.

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