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1 mol/L, polarization up to 0.2) induces numerous effects on proton and xenon NMR spectra. We show that the proton signal enhancements due to 129Xe–1H cross-relaxation (SPINOE) and overall shifts of the proton resonances due to the average dipolar shift created by the intense xenon magnetization are correlated. Protons behave as very useful sensors of the xenon magnetization. Indeed the xenon resonances exhibit many features such as superimposition of narrow lines on the main resonance due to clustering effects, or such as a polarization-dependent line broadening that is tentatively assigned to the effects of temperature fluctuations that decorrelate some distant dipolar field effects from local interactions, transforming xenon spins from “like” to “unlike” spins. These spectral features make difficult the determination of the average dipolar field by means of the xenon resonance but have interesting consequences on the heteronuclear polarization transfer experiment in Hartmann–Hahn conditions (SPIDER).
doi:10.1016/j.cplett.2004.08.050 
Copyright © 2004 Elsevier B.V. All rights reserved.
A continuously recirculating optical pumping apparatus for high xenon polarization and surface NMR studies
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Received 10 May 2004;
Abstract
A continuously recirculating xenon optical pumping apparatus was constructed and coupled to a 200 MHz NMR spectrometer. Steady-state 129Xe polarizations as high as 69% were achieved approximately 5 min after circulation was begun, and this polarization is >3.5 times larger than observed for single pass operation. Using this apparatus, spin polarization induced nuclear Overhauser effect (SPINOE) experiments were performed on porous silicon samples and on 13CD3OD adsorbed on TiO2-coated optical fibers to evaluate the capabilities of the system for studying low surface areas samples. The 13C enhancement achieved was approximately 14. The recirculating optical pumping system provides high xenon polarization at moderate laser powers for a variety of NMR studies.
