Charge and\nSpin Dynamics and Destabilization of Shallow\nNitrogen–Vacancy Centers under UV and Blue Excitation

Shallow\nnitrogen–vacancy (NV) centers in diamond\noffer opportunities\nto study photochemical reactions, including photogeneration of radical\npairs, at the single-molecule regime. A prerequisite is a detailed\nunderstanding of charge and spin dynamics of NVs exposed to the short-wavelength\nlight required to excite chemical species. Here, we investigate the\ncharge and spin dynamics of shallow NVs under 445 and 375 nm illumination.\nWith blue excitation, charge-state preparation is power-dependent,\nand modest spin initialization fidelity is observed. Under UV excitation,\ncharge-state preparation is power-independent and no spin polarization\nis observed. Aging of NVs under prolonged UV exposure manifests in\na reduced charge stability and spin contrast. We attribute this aging\nto modified local charge environments of near-surface NVs and identify\ndistinct electronic traps only accessible at short wavelengths. Finally,\nwe evaluate the prospects of NVs to probe photogenerated radical pairs\nbased on measured sensitivities and outline possible sensing schemes.