High Resolution Temperature-Resolved Spectroscopy of the Nitrogen-Vacancy 1E Singlet State Ionization Enenrgy

The negatively charged diamond nitrogen-vacancy (NV⁻) 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 ¹⁢E singlet state in the NV⁻ 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 ¹⁢E 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 ¹⁢E in the NV⁻ into the neutral NV⁰ 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 ¹⁢E 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.