Polarization relaxation of \(^{12}\)B in diamond

We have previously measured \(^{12}\) ${}^{12}$ B in single crystal diamond by \(\beta \) $\beta$ -NMR; however, the NMR signal was very weak, and approximately 90 \(\%\) $\%$ of implanted \(^{12}\) ${}^{12}$ B was undetected. In the present study, we measured the nuclear polarization and relaxation of \(^{12}\) ${}^{12}$ B implanted in grain-shaped diamonds at 15, 150, and 300 K. More than 20% of the implanted \(^{12}\) ${}^{12}$ 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 \(\beta \) $\beta$ -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.