%0 Conference Proceedings %B Proc. 12th Int. Zeolite Conf. %D 1999 %T Enhanced Surface NMR of Zeolites and Related Material Using Laser-Polarized Xenon %A Brunner, E. %A Haake, M. %A Pines, A. %A Reimer, J. %A Seydoux, R. %B Proc. 12th Int. Zeolite Conf. %P 2943-2950 %G eng %N 4 %! Enhanced Surface NMR of Zeolites and Related Material Using Laser-Polarized Xenon %0 Journal Article %J Journal of Magnetic Resonance %D 1999 %T Gas flow MRI using circulating laser-polarized Xe-129 %A Brunner, E. %A Haake, M. %A Kaiser, L. %A Pines, A. %A Reimer, J. A. %K xenon %X

We describe an experimental approach that combines multidimensional NMR experiments with a steadily renewed source of laser-polarized Xe-129. Using a continuous flow system to circulate the gas mixture, gas phase NMR signals of laser-polarized Xe-129 can be observed with an enhancement of three to four orders of magnitude compared to the equilibrium Xe-129 NMR signal. Due to the fact that the gas flow recovers the nonequilibrium Xe-129 nuclear spin polarization in 0.2 to 4 s, signal accumulation on the time scale of seconds is feasible, allowing previously inaccessible phase cycling and signal manipulation. Several possible applications of MRI of laser-polarized Xe-129 under continuous flow conditions are presented here. The spin density images of capillary tubes demonstrate the feasibility of imaging under continuous how. Dynamic displacement profiles, measured by a pulsed gradient spin echo experiment, show entry flow properties of the gas passing through a constriction under laminar flow conditions. Further, dynamic displacement profiles of Xe-129, flowing through polyurethane foams with different densities and pore sizes, are presented. (C) 1999 Academic Press.

%B Journal of Magnetic Resonance %V 138 %P 155-159 %8 May %@ 1090-7807 %G English %U ://WOS:000080303900021 %N 1 %M WOS:000080303900021 %! Gas flow MRI using circulating laser-polarized Xe-129 %R Doi 10.1006/Jmre.1998.1675 %0 Journal Article %J Journal of Physical Chemistry B %D 1999 %T NMR with a continuously circulating flow of laser-polarized Xe-129 %A Seydoux, R. %A Pines, A. %A Haake, M. %A Reimer, J. A. %K zeolites %X

In this paper we describe the construction of an apparatus for optical pumping of Xe-129 in a circulating gas system connected to a probe for static high-field NMR. The optimal working conditions for the optical pumping under flow are explored, yielding a continuous gas now with a steady-state spin-polarization of about 2%. It is shown that on various types of high surface area materials a steady-state of adsorbed laser-polarized xenon can be;reached with polarizations of about 0.3%. NMR spectroscopy of this layer is greatly facilitated due to the renewable magnetization under the continuous-flow conditions allowing unprecedented fast detection of two-dimensional NMR experiments with laser-polarized Xe. The steady-state spin-polarization of adsorbed Xe-129 gives rise to cross-relaxation to surface nuclei such as H-1 and Si-29. A direct spin-polarization-induced nuclear Overhauser effect (SPINOE) to heteronuclei is observed with an enhancement factor of about 20-30. A method is presented for simple modulation of the spin-polarization direction in the fringe field of the high-field magnet; this is exploited to obtain difference SPINOE spectra to highlight only the surface nuclei. Furthermore, a transfer via cross-polarization (CP) from adsorbed Xe to surface protons is demonstrated to select surface groups with reduced mobility compared to SPINOE detection.

%B Journal of Physical Chemistry B %V 103 %P 4629-4637 %8 Jun 3 %@ 1089-5647 %G English %U ://WOS:000080702600011 %N 22 %M WOS:000080702600011 %! NMR with a continuously circulating flow of laser-polarized Xe-129 %R Doi 10.1021/Jp9821984 %0 Journal Article %J Chemical Physics Letters %D 1998 %T Enhancement of C-13 NMR signals in solid C-60 and C-70 using laser-polarized xenon %A Brunner, E. %A Haake, M. %A Pines, A. %A Reimer, J. A. %A Seydoux, R. %K c60 %X

NMR signals emanating from surface nuclei of solids may be enhanced by the transfer of spin polarization from laser-polarized noble gases via SPINOE (spin polarization induced nuclear Overhauser effect). The present contribution describes experiments in which the spin polarization is transferred under magic angle spinning (MAS) from laser-polarized Xe-129 to C-13, a nuclear spin with a low gyromagnetic ratio in the fullerenes C-60 and C-70, polycrystalline materials with a low surface area. In C-70, differential enhancement of the NMR is observed for the different atomic sites in the molecule. (C) 1998 Elsevier Science B.V. All rights reserved.

%B Chemical Physics Letters %V 290 %P 112-116 %8 Jun 26 %@ 0009-2614 %G English %U ://WOS:000074466600018 %N 1-3 %M WOS:000074466600018 %! Enhancement of C-13 NMR signals in solid C-60 and C-70 using laser-polarized xenon %R Doi 10.1016/S0009-2614(98)00473-4 %0 Journal Article %J Chemical Physics Letters %D 1998 %T NMR of supercritical laser-polarized xenon %A Haake, M. %A Goodson, B. M. %A Laws, D. D. %A Brunner, E. %A Cyrier, M. C. %A Havlin, R. H. %A Pines, A. %K gas %X

The feasibility of producing supercritical laser-polarized xenon for nuclear magnetic resonance (NMR) investigations was studied. Using a high-pressure capillary tube, a supercritical xenon sample (52 degrees C, 65 atm) was produced with a Xe-129 polarization approximately 140 times the equilibrium value. The polarization was observed to last for hundreds of seconds, in agreement with previous studies. These preliminary results suggest that supercritical laser-polarized xenon may be used as a polarizing solvent for numerous NMR applications. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

%B Chemical Physics Letters %V 292 %P 686-690 %8 Aug 14 %@ 0009-2614 %G English %U ://WOS:000075482300049 %N 4-6 %M WOS:000075482300049 %! NMR of supercritical laser-polarized xenon %R Doi 10.1016/S0009-2614(98)00732-5 %0 Journal Article %J Journal of Magnetic Resonance %D 1998 %T Surface NMR using laser-polarized (129)Xe under magic angle spinning conditions %A Brunner, E. %A Seydoux, R. %A Haake, M. %A Pines, A. %A Reimer, J. A. %K flow %X

NMR signals of surface nuclei of solids may be enhanced by the transfer of spin polarization from laser-polarized noble gases. Until now such experiments have not been feasible under conditions of magic angle spinning. In the present contribution it is shown that laser-polarized (129)Xe can be inserted into a spinning rotor under continuous-flow conditions using helium as a carrier gas. Effective adsorption of xenon on the sample occurs at temperatures of about 163-173 K making possible the observation of a spin polarization induced nuclear Overhauser effect (SPINOE) from the laser-polarized (129)Xe to surface (1)H nuclei of SiO(2) (AEROSIL300). This technique opens the way to selectively enhanced high-resolution multinuclear surface NMR experiments. (C) 1998 Academic Press.

%B Journal of Magnetic Resonance %V 130 %P 145-148 %8 Jan %@ 1090-7807 %G English %U ://WOS:000072622700022 %N 1 %M WOS:000072622700022 %! Surface NMR using laser-polarized (129)Xe under magic angle spinning conditions %R Doi 10.1006/Jmre.1997.1296 %0 Journal Article %J Journal of the American Chemical Society %D 1997 %T Surface-enhanced NMR using continuous-flow laser-polarized xenon %A Haake, M. %A Pines, A. %A Reimer, J. A. %A Seydoux, R. %K solids %B Journal of the American Chemical Society %V 119 %P 11711-11712 %8 Dec 3 %@ 0002-7863 %G English %U ://WOS:A1997YK50200029 %N 48 %M WOS:A1997YK50200029 %! Surface-enhanced NMR using continuous-flow laser-polarized xenon %R Doi 10.1021/Ja9713587