  Treatment of lab-grown diamond by electron irradiation and annealing has
enabled quantum sensors based on negatively-charged nitrogen-vacancy
(NV$^\text{-}$) centers to demonstrate record sensitivities.
\cite{Clevenson2015,Wolf2015,Barry2016,Chatzidrosos2017}. Here we investigate
the irradiation and annealing process applied to 28 diamond samples using a new
ambient-temperature, all-optical approach. As the presence of the
neutrally-charged nitrogen-vacancy (NV$^\text{0}$) center is deleterious to
sensor performance, this photoluminescence decomposition analysis (PDA) is
first employed to determine the concentration ratio of NV$^\text{-}$ to NV$^0$
in diamond samples from the measured photoluminescence spectrum. The analysis
hinges on (i) isolating each NV charge state's emission spectrum and (ii)
measuring the NV$^\text{-}$ to NV$^0$ emission ratio, which is found to be
2.5$\pm$0.5 under low-intensity 532 nm illumination. Using the PDA method, we
measure the effects of irradiation and annealing on conversion of
substitutional nitrogen to NV centers. Combining these measurements with a
phenomenological model for diamond irradiation and annealing, we extract an
estimated monovacancy creation rate of $0.52\pm 0.26$ cm$^{\text{-1}}$ for 1
MeV electron irradiation and an estimated monovacancy diffusion coefficient of
1.8 nm$^2$/s at 850~$^\circ$C. Finally we find that irradiation doses $\gtrsim
10^{18}$ e$^\text{-}$/cm$^2$ deteriorate the NV$^\text{-}$ decoherence time
$T_2$ whereas $T_1$ is unaffected up to the the maximum investigated dose of
$5\times 10^{18}$ e$^\text{-}$/cm$^2$.
