A continuously recirculating optical pumping apparatus for high xenon polarization and surface NMR studies

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.