Skip to Main content Skip to Navigation
Theses

Effets des couplages dipolaires sur la précession RMN des liquides hyperpolarisés - Observations expérimentales dans le xénon et études numériques de modèles.

Abstract : In highly polarized dense liquids (such as water at equilibrium in high field for high resolution NMR, or optically hyperpolarized Xe-129 or He-3), the high magnetization density induces strong magnetic dipolar fields and the resulting non-linear couplings can deeply influence the spin dynamics. This thesis first presents an experimental study of dipolar couplings effects in a U-shaped sample of hyperpolarized liquid xenon (up to 6% polarization is obtained by optical pumping) ; the magnetization dynamics are studied by NMR in low magnetic field (1.5 mT). We then develop numerical models aiming at reproducing magnetization behaviors that have recently been observed in the experimental hyperpolarized systems; these general models can be applied to all cases when dipolar couplings play a role.

Both the experimental study and the numerical models show that the magnetization dynamics can strongly depend on parameters such as the shape of the sample, the tipping angle and the relative intensity between the dipolar fields and the spatial variations of applied fields. In anisotropic samples, at small tipping angle, the NMR spectra consist of sets of sharp lines ("spectral clustering"); in this case, the magnetization is described by independent magnetization modes. In all systems, at large tipping angle, the lifetimes can be extraordinarily shortened (by two orders of magnitude); this can be interpreted as a precession instability that results in disordered magnetization distribution.
Document type :
Theses
Complete list of metadatas

Cited literature [31 references]  Display  Hide  Download

https://tel.archives-ouvertes.fr/tel-00107453
Contributor : Pierre-Jean Nacher <>
Submitted on : Wednesday, October 18, 2006 - 5:39:26 PM
Last modification on : Monday, December 14, 2020 - 9:41:12 AM
Long-term archiving on: : Tuesday, April 6, 2010 - 6:00:29 PM

Identifiers

  • HAL Id : tel-00107453, version 1

Citation

François Marion. Effets des couplages dipolaires sur la précession RMN des liquides hyperpolarisés - Observations expérimentales dans le xénon et études numériques de modèles.. Matière Condensée [cond-mat]. Université Pierre et Marie Curie - Paris VI, 2002. Français. ⟨tel-00107453⟩

Share

Metrics

Record views

508

Files downloads

258