High Resolution Temperature-Resolved Spectroscopy of the Nitrogen Vacancy ^{1}E Singlet State Ionization Energy

The negatively charged diamond nitrogen-vacancy (NV^-) center plays a central role in many cutting edge quantum sensing applications; despite this, much is still unknown about the energy levels in this system. The ionization energy of the ¹E singlet state in the NV^-  has only recently been measured at between 2.25 eV and 2.33 eV. In this work, we further refine this energy by measuring the ¹E singlet state in the NV^- has only recently been measured at between 2.25 eV and 2.33 eV. In this work, we further refine this energy by measuring the  energy as a function of laser wavelength and diamond temperature via magnetically mediated spin-selective photoluminescence (PL) quenching; this PL quenching indicating at what wavelength ionization induces population transfer from the ¹E into the neutral NV⁰ charge configuration.  Measurements are performed for excitation wavelengths between 450 nm and 470 nm and between 540 nm and 566 nm in increments of 2 nm, and for temperatures ranging from about 50K to 150K in 5K increments. We determine the ¹E ionization energy to be between 2.29 and 2.33 eV, which provides about a two-fold reduction in uncertainty of this quantity. Distribution level: A. Approved for public release; distribution unlimited.