# Atmopsheric Gas IR-Spectra

I am looking for normal resolution IR-spectra of: $\ce{O2}$ and $\ce{N2}$ at high concentrations and; common minor gas in atmosphere: $\ce{H2O}$, $\ce{CO}$, and $\ce{CO2}$ at environmental concentrations. I have found some reference on internet (mostly from Green House Effect articles), but I cannot found it on a free, accurate and reliable source even on the free part of NIST databases.

Where can I find good references for such spectra? Thank you.

-

## 1 Answer

Completely symmetrical diatomic molecules like $\ce{O2}$ and $\ce{N2}$ are not IR-active because they have a zero dipole moment, even when oscillating within their one vibrational mode. Hence, there is no change in dipole moment possible, so these molecules will not be detectable by IR. The other molecules you mention, however, are IR-active, and I was able to find spectra of all three in the NIST database.

There are other spectroscopic methods that can detect IR-inactive molecules, however. Raman spectroscopy may be applicable, and I'm dimly aware of sophisticated methods based on absorptions in electronically excited states, but I don't know nearly enough about the subject to offer any concrete information on those techniques.

-
+1, marked as answer. I have missed the IR-Spectra check box. –  jlandercy Jul 15 '14 at 20:09
@jlandercy, ah, that's an easy mistake to make. Personally, I don't like the NIST search form very much. I often just use Google instead, along with a site:nist.gov query modifier. –  Greg E. Jul 15 '14 at 20:20
@ Greg E: Thanks for the advice. By the way, do you know a good article which address IR measurment technique non-linearity? –  jlandercy Jul 15 '14 at 20:23
@jlandercy, no, I'm sorry, I don't know of any off-hand. –  Greg E. Jul 15 '14 at 20:25