Assignment of the NV0 575 nm zero-phonon line in diamond to a 2E-2A2 transition

TL;DR

This paper identifies the 575 nm zero-phonon line in diamond's nitrogen-vacancy center as a 2E - 2A2 electronic transition, based on spectral analysis and electronic structure considerations.

Contribution

It provides the first assignment of the 575 nm transition to a 2E - 2A2 transition in the neutral nitrogen-vacancy center.

Findings

The 575 nm zero-phonon line is linked to a 2E - 2A2 transition.

Strain affects the splitting and polarization of zero-phonon lines similarly.

The excited state of the neutral NV center has A2 orbital symmetry.

Abstract

The time-averaged emission spectrum of single nitrogen-vacancy defects in diamond gives zero-phonon lines of both the negative charge state at 637 nm (1.945 eV) and the neutral charge state at 575 nm (2.156 eV). This occurs through photo-conversion between the two charge states. Due to strain in the diamond the zero-phonon lines are split and it is found that the splitting and polarization of the two zero-phonon lines are the same. From this observation and consideration of the electronic structure of the nitrogen-vacancy center it is concluded that the excited state of the neutral center has A2 orbital symmetry. The assignment of the 575 nm transition to a 2E - 2A2 transition has not been established previously.