I am currently doing some thermal/aerospace engineering research that involves finding light absorption in different points in Earth's orbit.

What is the best way to find absorbance vs. wavelength spectra data (IR,Vis,UV) for common gases such as O, O2, N2, He, Ar, etc.?

Ironically, I've found this spectra for other molecules, but am struggling with the most common gases on the planet. Help is much appreciated.

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    $\begingroup$ The homonuclear diatomics have no (or at least v. v. small) ir absorption (due to selection rules) so you will need to look for Raman spectra to get wavelengths, but they do have uv absorption. There should be lots of sites giving this (Search for images of spectra) otherwise look at the NIST site. Atomic energy levels can be found easily also. $\endgroup$
    – porphyrin
    Jul 6, 2023 at 7:32

2 Answers 2


You will need to use some chemical intuition and the right keywords. He and Ar (and all other noble gases) are monoatomic, so it is good omen that one cannot find their vibrational spectra. Similarly, these gases are colorless, so there will be no absorbance in the visible region. There are no double or triple bonds in noble gases, one will not expect an ordinary UV spectrum. However, you will need to search deep UV or vacuum UV absorption spectrum of these gases which must have been studied to the hilt.

Coming to diatomic gases (oxygen and nitrogen), since there is no dipole moment change during vibration of a homonuclear diatomic gas, we do not expect an infrared spectrum of these gases. These molecules do vibrate, should one look for a Raman spectrum then?

(Liquid) oxygen is somewhat pale blue, so it means that gaseous oxygen will absorb light in the deep red region. We can see those beautiful absorption bands in high resolution solar spectrum. Search high resolution solar spectrum. Diatomic oxygen and nitrogen both absorb deep UV at the cost of being broken or ionized (recall ozone formation).

  • $\begingroup$ gaseous O2 has no visible spectrum at least at reasonable low pressure. There is purported weak dimerization in the liquid and solid that absorbs. The blue in water is dfferent that is a stretch overtone so is present in liquid and gas. $\endgroup$
    – jimchmst
    Jul 6, 2023 at 21:28
  • $\begingroup$ Actually, gaseous oxygen at 1 bar pressure does absorb near IR and red, to some extent. These give rise to the so-called “telluric” bands that astronomers and astro-spectroscopists take into account when they acquire spectra. See also chemistry.stackexchange.com/q/15035/79678. $\endgroup$
    – Ed V
    Jul 7, 2023 at 12:31
  • $\begingroup$ And the Fraunhofer A “line” is due to atmospheric oxygen absorption around 760 nm: astronomy.stackexchange.com/a/18034/45954. So the answer is fine. $\endgroup$
    – Ed V
    Jul 7, 2023 at 13:41

For UV-Vis, one source is The MPI-Mainz UV/VIS Spectral Atlas of Gaseous Molecules of Atmospheric Interest mentioned in an earlier answer. Given the (chemical) simplicity of the compounds of interest mentioned, NIST Chemistry WebBook can complement this one; this compilation includes IR data e.g. about gaseous carbon dioxide

enter image description here

(image credit to NIST, screen photo from here)

in formats you can process further (e.g., JCAMP-DX).


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