Nitrogen-Vacancy Energy Levels
Laser excitation (480-640nm) of the NV center results in optical excitation of electrons into an excited state. The electrons quickly decay to ground state by emitting a photon (638-800nm) or through a non-radiative process. Negatively charged centers (NV-) have a ground and excited triplet-state consisting of spin-projections ms=0 and ±1.
Applying radio frequency (RF) radiation, such as microwave radiation, at a resonant frequency (2.87 GHz, zero-field splitting), causes the redistribution of electrons between the ground states. At zero magnetic field, the +1 and -1 states are degenerate (have the same energy). An external magnetic field lifts the spin degeneracy, splitting the two apart.Electrons excited from ground state 0 emit photons to revert with a high probability to the same ground state. Electrons excited from ground state +/-1 can become temporarily trapped in a dark “singlet” state before non-radiative decay with a high probability to ground state 0.
With a high probability, electrons excited from ground state 0 emit photons to revert to the same ground state. Electrons excited from ground state +/-1 can become temporarily trapped in a dark “singlet” state before non-radiative decay to ground state 0. Therefore, fluorescence emissions can be controlled by or monitored to detect the presence of external RF radiation or magnetic field.