&& EPR && & [@DHaenens-Johansson2011]\
[$\mathrm{SiV}^{-}$]{} && UV-vis && & [@DHaenens-Johansson2011]\
[$\mathrm{SiVN}^0$]{} && EPR &&\

\[tab:quantification\_methods\]

Analagous to the well-known aggregation of nitrogen-vacancy centers in diamond ($\mathrm{N}_n\mathrm{V}$, where $n=\numrange{1}{4}$) [@Evans1982], we observe the aggregation of $\mathrm{N}_n\mathrm{VH}$ as the annealing temperature increases. A decrease in [$\mathrm{NVH}$]{} at $\geq\SI{1800}{\celsius}$ and above is accompanied by an increase in [${\ensuremath{\mathrm{N_2VH}}\xspace}^{0}$]{}, which in turn decreases at with a corresponding rise in [${\ensuremath{\mathrm{N_3VH}}\xspace}^{0}$]{} \[Fig \[fig:annealing\]\].

The majority of the sharp IR one-phonon and C-H stretch absorption peaks observed in [Sample A]{}\[Fig. \[fig:ir\_comparison\]a)\] have been previously observed in high-nitrogen, high-hydrogen brown diamond from several sources [@Wang2007; @Khan2010], and their photochromic behavior reported [@Khan2010]. The point defect origin of these peaks has not been identified, but they do not appear to require silicon. However, the small shoulder at is not present in previous reports of high-nitrogen material. The peak itself is not photochromic, and its frequency does not depend on nitrogen isotope. Samples grown under similar conditions but without the addition of silicon to the growth gasses produce similar one-phonon spectra except for the absence of the mode \[Fig. \[fig:ir\_comparison\](b)\]. Previous DFT calculations predict a mode originating at the carbon atoms surrounding substitutional silicon at [@Goss2007]: in conjunction 