Spectroscopy of photoionization from the
1E singlet state in nitrogen
−vacancy centers in diamond
The
1E−1A1 singlet manifold of the negatively charged nitrogen vacancy
(NV−) center in diamond plays a central role in the quantum information and quantum sensing applications of the
NV− center. However, the energy of this manifold within the diamond bandgap and with respect to the
3A2−3E triplet manifold has not been measured directly. Using field-quenching effects on photoluminescence (PL) spectra, we report on the energy gap between the
1E−1A1 singlet manifold and the
3A2 and
3E ground and excited triplet states of the
NV− as a function of excitation wavelength and power, temperature, and applied magnetic field in a heavily nitrogen-doped sample. Increased PL and decreased zero-phonon line width from the
NV0 were observed in the presence of an applied magnetic field, indicating ionization from the long-lived
1E singlet state. A temperature-dependent ionization threshold between 532 nm and 550 nm was found, locating the singlet states within the diamond band gap.
The
1E--
1A1 singlet manifold of the negatively charged nitrogen vacancy ($\mathrm{N}{V}^{\ensuremath{-}}$) center in diamond plays a central role in its quantum-information and quantum-sensing applications. However, the energy gap between the
1E singlet state and diamond band edges or the
3A2--
3E triplet manifold has not been measured directly. Using the magnetic-field quenching effect on the $\mathrm{N}{V}^{\ensuremath{-}}$ photoluminescence (PL) spectra, we measure these energy gaps as a function of temperature, applied magnetic field, excitation wavelength, and excitation power in a heavily nitrogen-doped sample. Increased PL and decreased zero-phonon line width from the
NV0 center were observed in the presence of an applied magnetic field, indicating ionization from the long-lived
1E singlet state. A temperature-dependent ionization threshold between 532 and 550 nm was found, locating the singlet states within the diamond band gap.
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.