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CS Absorption at Ultraviolet Wavelengths from Diffuse Molecular Gas

Presentation #147.06 in the session Laboratory Astrophysics (LAD) Division Meeting: iPoster Session.

Published onJun 29, 2022
CS Absorption at Ultraviolet Wavelengths from Diffuse Molecular Gas

We reexamine the abundance of CS in diffuse molecular clouds from lines in the C-X (0, 0) band near 1400 Å seen in spectra acquired with the Hubble Space Telescope. We include additional sight lines not available in previous work and extract information on molecular structure. The analysis incorporates results from our recent large-scale calculations on CS photodissociation and adopts the approach taken in our study of the F-X (0, 0) and (1, 0) bands in C2. Syntheses of the high-resolution spectra with the best signal to noise yielded wavelengths for the R(0), R(1), and P(1) lines and their widths. Significant line broadening is seen; the inferred predissociation width is within a factor of 2 of the predictions from the calculations. The computations also revealed similar rotational constants for the X and C states. The differences in transition frequencies among the three lines then suggest a shift for the P(1) line. We also found evidence that the strengths for the R(1) and P(1) lines were affected by the perturbation. The fits for detections in other directions adopted these refined line parameters to determine column densities. A comparison of the CS column densities with results for CH, CN, CO, and H2 helped inform us of the chemical pathways leading to CS in diffuse molecular gas. A simple chemical network is able to reproduce the observations within a factor of 2 for most sight lines.

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