On the Possibility of Detecting Molecular Hydrogen and Nitrogen in Planetary and Stellar Atmospheres by Their Rotation-Vibration Spectra

Abstract

view Abstract Citations (39) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Possibility of Detecting Molecular Hydrogen and Nitrogen in Planetary and Stellar Atmospheres by Their Rotation-Vibration Spectra Herzberg, Gerhard Abstract The detection of molecular hydrogen and nitrogen in planetary or stellar spectra, hitherto deemed impossible, can be carried out by means of the rotation-vibration spectrum of these molecules. Though H2 and N2, as is well known, have no ordinary rotation-vibration spectra (since their dipole moment is zero), they do have rotation- vibration spectra, owing to their quadrupole moment. In the case of H2 the i -o band of this quadrupole rotation-vibration spectrum, according to calculations of James and Coolidge, is 8.1 X io-9 times as intense as the i-a band of the ordinary rotation-vibration spectrum of HC1. The minimum absorb- ing layer necessary to detect the I -0, 2-0, and 3-0 bands is found to be 2.5, 2.7, and `3.0 km aim., respectiveiy. This is of the order of magnitude probably available in the atmospheres of the major planets. A table of the positions of the lines of the i -o. 2-0, 3-0, and 4-0 bands as predicted from the ultraviolet H2 spectrum is given. The band most favorable for detection is the 3-0 band at 8~oo A. Failure to observe this band would at least give an upper limit for the amount of H2 present in the atmos- pheres of the major planets or of low-temperature stars. For N2 the predicted positions of the Q branches of the bands are given. Their de- tection will probably be more difficult than the detection of the H2 bands. A further possibility of detecting molecular hydrogen and nitrogen is by the ordinary rotation-vibration spectrum of the isotopic molecules HD and 1V'4LV'~, which are always present in natural hydrogen and nitrogen, respectively Publication: The Astrophysical Journal Pub Date: May 1938 DOI: 10.1086/143935 Bibcode: 1938ApJ....87..428H full text sources ADS |