Polarization relaxation of ^12 B in diamond

We have previously measured ^12 B in single crystal diamond by β -NMR; however, the NMR signal was very weak, and approximately 90 % of implanted ^12 B was undetected. In the present study, we measured the nuclear polarization and relaxation of ^12 B implanted in grain-shaped diamonds at 15, 150, and 300 K. More than 20 ^12 B nuclei were found to initially settle at sites that maintained polarization well, and polarization relaxation in the order of tens of milliseconds was observed. This partially explained the very weak β -NMR signal in the previous experiment. A slow relaxation was observed at 15 K in addition to the fast relaxation. The existence of these two relaxations suggested multiple implantation sites.