High Resolution Temperature‐Resolved Spectroscopy of the Nitrogen‐Vacancy ¹ E Singlet State Ionization Energy

The negatively charged diamond nitrogen‐vacancy () center plays a central role in many quantum sensing applications, though much is still unknown about the energy levels in this system. The ionization energy of the singlet state in the center has only recently been measured to be between 2.25 and 2.33 eV. In this work, we reduce this uncertainty by measuring the ionization energy as a function of excitation laser wavelength and diamond temperature via magnetically mediated spin‐selective photoluminescence (PL) quenching that transfers population from the in the into the neutral charge configuration. Measurements are performed for excitation wavelengths between 450 and 470 nm, and between 540 and 566 nm in increments of 2 nm, and for temperatures ranging from about 50 to 150 K in 5 K increments. We determine the ionization energy to be between 2.29 and 2.33 eV, which provides about a twofold reduction in uncertainty of this quantity. Distribution level: A. Approved for public release; distribution unlimited.