Open AccessOn the detection of interstellar homonuclear diatomic molecules
Author(s) -
Ruffle D. P.,
Williams D. A.,
Duley W. W.
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.01424.x
Subject(s) - homonuclear molecule , diatomic molecule , physics , atomic physics , ionization , interstellar cloud , excitation , astrophysics , interstellar medium , emission spectrum , molecule , astronomy , spectral line , galaxy , ion , quantum mechanics
The pure rotational spectrum of homonuclear diatomic molecules in the interstellar medium is strongly forbidden, and no such spectrum has been detected. In regions of high excitation, vibrational emission may occur, as is widely detected in the case of H 2 in interstellar shocks and photon‐dominated regions. However, it is of considerable interest to know the abundance of homonuclear diatomics in quiescent regions. We propose that vibrational emission from homonuclear diatomic molecules in cold clouds may be detectable, where the excitation is mainly through collisions with non‐thermal electrons arising from the cosmic‐ray ionization of H 2 . As an example, we estimate the intensity of emission from N 2 in cold, dark interstellar clouds. We show that such emission is at the limit of detectability with current technology. Other excitation mechanisms may also contribute and enhance this emission.