“Nitrogen”, without any other specifier, and when not talking about fertilizer, typically refers to dinitrogen. I doubt very much that it’s single nitrogen atoms (since those don’t really float around freely). If it were a nitrogen-containing compound, I don’t see why it wouldn’t be referred to by that compound’s name.
The wiki article mentions that removal of nitrogen decreases growth rate and increases inclusion frequency. The J. Appl. Phys. article they cite mentions that the crystals were grown from an H2 CH4 N2 mix.
I would never assume that nitrogen used without a modifier assumes nitrogen gas in laypersons discusion. The J. Appl. Physics article you mention is with regard to chemical vapor deposition diamonds. CVD diamonds do not suffer from the color problems that the HPHT diamonds produced by Gemesis do.
The Gemesis method uses a proprietary catalyst, which I assume is metallic in nature. Nitrogen is an excellent sigma donor to stabilize metallic compounds, so I thought perhaps the nitrogen was in the catalyst. Proprietary rights would be one reason that they do not tell you the source of the nitrogen.
Even if the source of the nitrogen is N2, I don’t think N2 in the structure that causes the yellow color. There is enough energy going into the process to split N2 and then some. N2 is not at all a colorfull compound, and while there are always bizaar electronics in strange circumstances, I think it is more likely lone nitrogen atoms in the matrix similar to doped silicon.
I think he means they fluoresce for a short time after being exposed. Which would really be phosphorescence; I don’t think diamonds have that property, though.
Since the starting form of carbon is graphite (or amorphous carbon), I’d guess that the fluorescence comes from incomplete conversion of polyaromatic hydrocarbons stuck in nanometer defects. I guess they wouldn’t be hydrocarbons, but small sections of graphite that exhibit similar electronics to PAH’s.
That’s a guess though. Ruken is the guy with literature access right now.
About a third of all diamonds fluoresce under UV light. Some a slight bit, some intense. This is caused by trace impurities trapped in the diamond when it was made.
I’ve examined diamonds which look “milky” under store lights, but always fluoresce when put under UV. The “milkier” the diamond looks, the more it will fluoresce.