tra, indicating a common tie among them, namely
the presence of the common N3 center and the lack
of more dominant fluorescing defects or significant
concentrations of defects that can quench fluorescence,
such as the A aggregate (Davies and
Crossfield, 1973; Davies et al., 1974).
The category 1 fluorescence spectrum is associated
with the N3 center, as is the subordinate peak at
~450 nm in the categories 2 and 3 fluorescence spectra
(i.e., figures 5 and 8). This feature was seen in
most of the diamonds, both natural and treated color.