We have a laser chamber full of $\ce{F2}$ gas (no air should be in the chamber) and several parts including steel, wires, ceramics, zinc.... This is for laser generation so the temperature is pretty high in the chamber. We have detected $\ce{NO2}$ gas in our FTIR specturm which caused our laser to fail and there’s a good chance that the $\ce{NO2}$ may be associated with the failure. The questions are

  • How might $\ce{NO2}$ be formed in a chamber? If it’s from air, why would $\ce{NO2}$ be formed and not $\ce{NO}$ or $\ce{N2O}$? Why would $\ce{NO2}$ persist after $\ce{N2}$ and $\ce{O2}$ are removed by chamber refills with fresh $\ce{F2}$?

  • How does $\ce{NO2}$ interact with fluorine? What other species might be formed when they react?

  • Can $\ce{NO2}$ be dissociated by UV light (i.e. 193 nm)? What is its UV absorption spectrum?

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    $\begingroup$ I'd guess that you have an air leak. "Flushing" only helps if the source of the $\ce{NO_2}$ is fixed. $\ce{O_2}$ would definitely be dissociated by a 193nm laser to produce two oxygen free radicals. Normally with extra oxygen that would make ozone. I'm guessing that the oxygen must be low in concentration and nitrogen relatively high. So perhaps most of the oxygen is $\ce{OF_2}$? So $[F_2] >> [N_2] >> [O_2]$ $\endgroup$ – MaxW Oct 31 '15 at 23:42
  • $\begingroup$ If you somehow manage to get nitrogen to react with oxygen, as long as there is oxygen present, $\ce{NO}$ will combine to form $\ce{NO2}$, especially at high temperatures. $\ce{NO}$ is the most likely primary reaction product, because it is even harder to form $\ce{N2O}$ from $\ce{N2}$ with oxygen iirc. I can’t help you on the other questions but I would be greatly surprised if no-one could find a UV spectrum. $\endgroup$ – Jan Nov 1 '15 at 1:16

Fluorine reacts with practically everything, especially at high temperatures, including zinc, wires, some ceramics, polymers, etc., so the system you describe may be prone to contamination. I don't see any obvious source of NO2, but it could easily form from nitrates, if present, in an acidic environment, which could result from fluorine attacking metals present.

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