NMR instabilities in highly magnetised liquid helium solutions

Spin dynamics have been shown to be dramatically altered in anisotropic samples when the internal dipolar field dominates the external static field gradients. In recent NMR experiments on laser polarised liquids (He or Xe), spectral clustering and precession instabilities have been observed. Early a...

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Bibliographic Details
Published in:Journal of low temperature physics 2002, Vol.126 (1-2), p.145-150
Main Authors: NACHER, Pierre-Jean, PIEGAY, Nathalie, MARION, Francois, TASTEVIN, Geneviève
Format: Article
Language:English
Subjects:
Atomic Physics
Condensed matter: structure, mechanical and thermal properties
Exact sciences and technology
Mixed systems
liquid 3He, 4He mixtures
Physics
Quantum fluids and solids
liquid and solid helium
Spin-polarized hydrogen and helium
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Summary:Spin dynamics have been shown to be dramatically altered in anisotropic samples when the internal dipolar field dominates the external static field gradients. In recent NMR experiments on laser polarised liquids (He or Xe), spectral clustering and precession instabilities have been observed. Early analyses have suggested the generic nature of these effects, and tentatively addressed their existence in bulk systems. We report here on. NMR. experiments conducted in spherical samples of laser-polarised liquid helium mixtures (0.5-10% He-3 in He-4 at 1-2K). We focus on the relative influence of magnetisation density and applied field gradients on FID signals induced by 90degrees tipping pulses. Numerical simulations are used to study the effects of distant dipolar couplings on local and global magnetisation. A discussion of the features of FID and spin echo signals is presented.
ISSN:0022-2291
1573-7357
DOI:10.1023/A:1013787405665