# Electron paramagnetic resonance and photochromism of $\mathrm{N}_{3}\mathrm{V}^{0}$ in diamond

## TL;DR

This study characterizes the electron paramagnetic resonance and photochromic behavior of the N3V defect in diamond, providing refined models and insights into charge transfer mechanisms relevant for diamond-based quantum technologies.

## Contribution

The paper offers the first accurate simulation of N3V0 EPR spectra for arbitrary magnetic fields and reveals charge transfer processes involving N3V in diamond.

## Key findings

- Refined spin Hamiltonian parameters for N15N3V0.
- Successful simulation of N14N3V0 spectra for any magnetic field orientation.
- Evidence of charge transfer between N3V and substitutional nitrogen under light excitation.

## Abstract

The defect in diamond formed by a vacancy surrounded by three nearest-neighbor nitrogen atoms and one carbon atom, $\mathrm{N}_{3}\mathrm{V}$, is found in $\approx98\%$ of natural diamonds. Despite $\mathrm{N}_{3}\mathrm{V}^{0}$ being the earliest electron paramagnetic resonance spectrum observed in diamond, to date no satisfactory simulation of the spectrum for an arbitrary magnetic field direction has been produced due to its complexity. In this work, $\mathrm{N}_{3}\mathrm{V}^{0}$ is identified in $^{15}\mathrm{N}$-doped synthetic diamond following irradiation and annealing. The $\mathrm{^{15}N}_{3}\mathrm{V}^{0}$ spin Hamiltonian parameters are revised and used to refine the parameters for $\mathrm{^{14}N}_{3}\mathrm{V}^{0}$, enabling the latter to be accurately simulated and fitted for an arbitrary magnetic field direction. Study of $\mathrm{^{15}N}_{3}\mathrm{V}^{0}$ under excitation with green light indicates charge transfer between $\mathrm{N}_{3}\mathrm{V}$ and $\mathrm{N_s}$. It is argued that this charge transfer is facilitated by direct ionization of $\mathrm{N}_{3}\mathrm{V}^{-}$, an as-yet unobserved charge state of $\mathrm{N}_{3}\mathrm{V}$.