Scott, E., M. Drake, and J.A. Reimer, The phenomenology of optically pumped 13C NMR in diamond at 7.05 T: Room temperature polarization, orientation dependence, and the effect of defect concentration on polarization dynamics. J. Magn. Reson., 2016. 264: p. 154-162.
Room temperature optical illumination of NV− imbibed single crystal diamonds with a 532 nm laser produces 13C polarization enhancements up to 200 times greater than that of the thermal equilibrium value at 7.05 T. We report high field NV− mediated 13C polarization as a function of the number and type (NV− and P1) of defects in commercially available diamonds. Surprisingly, both positive and negative 13C polarizations are observed depending on the orientation of the crystal with respect to the external magnetic field and the electric field vector of the optical illumination. The data reported herein cannot be explained by a previously proposed mechanism.