Bulk 13C polarization can be strongly enhanced in diamond at room-temperature based on the optical pumping of nitrogen-vacancy color centers. This effect was confirmed by irradiating suitably aligned single-crystals at a ~50 mT field promoting anti-crossings between electronic excited-state levels, followed by shuttling of the sample into a custom-built NMR setup and by subsequent 13C detection. A nuclear polarization of ~0.5% - equivalent to the 13C polarization achievable by thermal polarization at room temperature at fields of ~2000 T - was measured, and its bulk nature determined based on line shape and relaxation measurements. Positive and negative enhanced polarizations were obtained, with a generally complex but predictable dependence on the magnetic field during optical pumping. Owing to its simplicity, this 13C room-temperature polarizing strategy provides a promising new addition to existing nuclear hyperpolarization techniques.
@article{arxiv.1211.5801,
title = {Bulk Nuclear Polarization Enhanced at Room-Temperature by Optical Pumping},
author = {Ran Fischer and Christian O. Bretschneider and Paz London and Dmitry Budker and David Gershoni and Lucio Frydman},
journal= {arXiv preprint arXiv:1211.5801},
year = {2013}
}