  We model the decoherence and dephasing of nitrogen vacancy (NV) centers in
diamond due to a noisy paramagnetic bath, with and without the presence of a rf
field that couples levels of the ground electronic state manifold, using a
simple quantum mechanical model that allows for analytical solutions. The model
treats the NV three-level ground state system in the presence of fluctuating
magnetic fields that arise from the environment, and that result in
decoherence, dephasing and dissipation. We show that all 9 eigenmodes of the
three-level system are coupled to each other due to interaction with the
environment, and we discuss consequences for fitting experiments in which
decoherence plays a role.
