Bulk Nuclear Polarization Enhanced at Room-Temperature by Optical Pumping

TL;DR

This paper demonstrates a method to enhance bulk 13C nuclear polarization in diamond at room temperature using optical pumping of nitrogen-vacancy centers, achieving significant polarization levels with potential applications in hyperpolarization.

Contribution

The study introduces a novel room-temperature bulk polarization technique in diamond via optical pumping of NV centers, expanding hyperpolarization methods.

Findings

Achieved ~0.5% 13C polarization at room temperature.

Confirmed bulk nature of polarization through line shape analysis.

Demonstrated complex dependence of polarization on magnetic field.

Abstract

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.