%0 Journal Article %J Physical Review A %D 1994 %T Multiple-Pulse Nuclear-Magnetic-Resonance of Optically Pumped Xenon in a Low Magnetic-Field %A Raftery, D. %A Long, H. W. %A Shykind, D. %A Grandinetti, P. J. %A Pines, A. %K ne-21 %X
Multiple-pulse coherent averaging methods are used to increase the resolution and frequency range of optically pumped xenon NMR in nutation and point-by-point precession experiments. We observe quadrupolar splittings in Xe-131 spectra due to the macroscopic asymmetry of pumping cells similar to those reported previously, but with reduced demands on magnetic-field homogeneity. Cell treatment with hydrogen gas increases the quadrupolar splittings by a factor of 3 over bare Pyrex cells.
%B Physical Review A %V 50 %P 567-574 %8 Jul %@ 1050-2947 %G English %UA method for NMR studies of low surface area materials using optically pumped xenon gas is described. The method has been used to investigate spin-polarized xenon adsorbed onto poly(acrylic acid). The temperature dependence of the xenon-surface interaction, as measured by the xenon chemical shifts extrapolated to zero pressure, is shown to be consistent with a simple model of chemical exchange between the gas and adsorbed phases. The magnitude of the surface contribution to the Xe-129 chemical shift indicates a relatively strong interaction between xenon and poly(acrylic acid), possibly due to the polar carboxylic acid functional groups at the polymer surface. From the pressure dependence of the Xe-129 shift, the diffusion coefficient of xenon on poly(acrylic acid) is estimated to be 3.3 x 10(-5) cm2/s.
%B Journal of Physical Chemistry %V 97 %P 1649-1655 %8 Feb 25 %@ 0022-3654 %G English %UNMR of Xe-129 has been observed in thin films of xenon frozen onto the surfaces of glass sample cells with various geometries. The Xe-129 polarization was enhanced by optical pumping, and the xenon was then transferred to a high-field pulsed NMR spectrometer allowing the observation of strong signals from xenon films of approximately 1-mu-m thickness. The line shape depends on the film geometry because of the bulk diamagnetic susceptibility chi(D) of solid xenon. The spectral line shape and resonance frequency also depend on temperature.
%B Chemical Physics Letters %V 191 %P 385-390 %8 Apr 10 %@ 0009-2614 %G English %UOptical pumping has been used to enhance the pulsed NMR signal of Xe-129, allowing the detection of low-pressure xenon gas and of xenon adsorbed on powdered solids. We observe an increase in sensitivity of more than 2 orders of magnitude over conventional NMR, the current limitation being the laser power. Adsorbed xenon is observed at 298 K on graphitized carbon (10 m2/g) and on powdered benzanthracene (approximately 0.5 m2/g) below 170 K. The increased sensitivity of this technique allows the study of a large class of amorphous materials with surface areas below 10 m2/g including semiconductors, polymers, metal oxides, and catalysts.
%B Physical Review Letters %V 66 %P 584-587 %8 Feb 4 %@ 0031-9007 %G English %UXe-129 NMR spectroscopy has been used to probe directly the distribution of xenon atoms confined in atomic-size Na-A zeolite cavities. For mean xenon occupancies less than about three Xe atoms per a-cage, the guest populations are well described by binomial statistics. At higher guest loadings the finite volumes of the xenon atoms become significant, as reflected by a fit of the experimental populations with a hypergeometric distribution, with a maximum of seven Xe atoms per cage. At the highest xenon loadings the experimental distribution is narrower than hypergeometric, as predicted by Monte Carlo simulations.
%B Physical Review Letters %V 66 %P 580-583 %8 Feb 4 %@ 0031-9007 %G English %U