%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