Cross Polarization from Laser-Polarized Solid Xenon to (Co2)-C-13 by Low-Field Thermal Mixing

The first observation of nuclear spin polarization enhancement in a molecular species by coupling to laser-polarized xenon is reported. The spins of (CO2)-C-13 were cooled by inclusion into the xenon solid followed by thermal mixing in magnetic fields comparable to the heteronuclear dipolar interactions. High-field NMR detection yielded enhancement factors of up to 200. Moreover, a change in the sense of the helicity of the optical pumping light results in a sign reversal of the spin temperature and hence an inversion of the C-13 NMR signal.