FURTHER EVIDENCE FOR THE IDENTIFICATION OF INTERSTELLAR ABSORPTION LINES IN TERMS OF $H_{2}$ TRANSITIONS
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Date
1975
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Publisher
Ohio State University
Abstract
A total of fourteen lines which appear in the interstellar absorption spectrum, and which vary in half-width between 1 \AA and 5 \AA, have been identified in terms of allowed transitions from electronically excited $H_{2}$. These relatively sharp lines, which hove been detected by Herbig and others in the spectrum of the same interstellar medium which gives rise to the more well-known broad absorption bands (e.g., 4430 {\AA}), are classified according to lower state and upper state. Thirteen lines have their origin in various vibrational-rotational levels of the $B^{1}\Sigma^{+}_{u}$ electronic state and one originates in the $v = 1$, $J = 1$ level of the $C^{1}\Pi_{u}$ state. The upper state assignments are consistent with all selection rules and the absorption wavelengths are in essentially exact agreement with Dieke’s emission measurements. The energies of the lower states involved in the absorption strongly suggest selective, near-resonance pumping by collisional and radiative processes which involve atomic Lyman quanta. This model gives further support to the $theory^{1}$ that the broader absorption bands correspond to analogous transitions into the predissociative continuum of $H_{2}$. Probable assignments for the broad bands, including 4430 A, are also given.
Description
$^{1}$ J. A. Duardo, Interstellar $H_{2}$ Narrow and Diffuse Line Absorption"", Twenty-Ninth Symposium on Molecular Structure and Spectroscopy, The Ohio State University, June, 1974.""""
Author Institution: Xerox Electro-Optical Systems
Author Institution: Xerox Electro-Optical Systems