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In this paper we describe the construction of an apparatus for optical pumping of ¹²⁹Xe 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 flow 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 ¹²⁹Xe gives rise to cross-relaxation to surface nuclei such as ¹H and ²⁹Si. 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.

The chemical shifts and relaxation times T1 and T2of 3He and 129Xe nuclei of noble gas atoms as well as those of 7Li and 133Cs nuclei of isoelectronic Li+and Cs+ions have been measured in aqueous solutions, which contain paramagnetic Mn2+and Co2+ions. The magnetic relaxation of all studied nuclei in Co2+solutions proceeds via an electronic spin relaxation of these ions. The relaxation in Mn2+solutions is determined by the translational diffusion of the solute particles. The closest approach distances for collisions of paramagnetic ions with atoms of noble gases and alkali ions were estimated from relaxation data.