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arXiv · 1211.0844

Ultraviolet Measurements of Interstellar C2

Ryan C. Hupe·Y. Sheffer·S. R. Federman
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Abstract

We analyzed archival spectra acquired with the Hubble Space Telescope for a study of interstellar C2. Absorption from the electronic transitions, D ^1Sigma^+_u -- X ^1Sigma^+_g (0,0) as well as F ^1Pi_u -- X ^1Sigma^+_g (0,0) and (1,0), was the focus of the study. Our profile syntheses revealed that the lines of the F-X bands were broadened as a result of a perturbation involving the upper levels. Further evidence for the perturbation came from anomalies in line strength and position for the F-X (0,0) band. The perturbation likely arises from a combination of triplet-singlet interactions involving spin-orbit mixing between ^3Pi_u states and F ^1Pi_u and an avoided crossing between the ^3Pi_u states. Tunneling through a potential barrier caused by the 3 and 4 ^1Pi_u states and spin-orbit mixing with other close-lying triplet states of ungerade symmetry are less likely. Except for the broadening, lines in the F-X (1,0) band appear free from anomalies and can be used to study interstellar C2; new results for 10 sight lines are presented.

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Ryan C. Hupe, Y. Sheffer, S. R. Federman. 2012-11-05. Ultraviolet Measurements of Interstellar C2. https://doi.org/10.1088/0004-637x%2F761%2F1%2F38

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