Rovibrational Transitions in HCl due to Collisions with H2: Spin-free and Hyperfine-resolved Transitions

Hydrogen chloride (HCl) is a key repository of chlorine in the interstellar medium. Accurate determinations of its abundance are critical to assessing the chlorine elemental abundance and constraining stellar nucleosynthesis models. To aid in modeling recent and future observations of HCl rovibratio...

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Bibliographic Details
Published in:The Astrophysical journal 2024-07, Vol.969 (1), p.7
Main Authors: Hoffman, Daniel, Taylor, Josiah, Price, T. J., Forrey, Robert C., Yang, B. H., Stancil, P. C., Zhang, Z. E., Balakrishnan, N.
Format: Article
Language:English
Subjects:
Abundance
Astrochemistry
Astronomical models
Chlorine
Chlorine compounds
Coefficients
Collision physics
Collisions
Cross-sections
De-excitation rates
Hydrogen chloride
Interstellar chemistry
Interstellar matter
Interstellar medium
Molecular data
Molecular physics
Nuclear fusion
Radiative transfer
Small molecules
Stellar models
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Summary:Hydrogen chloride (HCl) is a key repository of chlorine in the interstellar medium. Accurate determinations of its abundance are critical to assessing the chlorine elemental abundance and constraining stellar nucleosynthesis models. To aid in modeling recent and future observations of HCl rovibrational spectra, we present cross sections and rate coefficients for collisions between HCl and molecular hydrogen. Transitions between rovibrational states of HCl are considered for temperatures ranging from 10 to 3000 K. Cross sections are computed using a full dimensional quantum close-coupling (CC) method and a reduced dimensionality coupled-states (CS) approach. The CS results, benchmarked against the CC results, are used with a recoupling approach to calculate hyperfine-resolved rate coefficients for rovibrational transitions of HCl induced by H2. The rate coefficients will allow for a better determination of the HCl abundance in the interstellar medium and an improved understanding of interstellar chlorine chemistry. We demonstrate the utility of the new rate coefficients in a nonthermodynamic equilibrium radiative transfer model applied to observations of HCl rovibrational transitions in a circumstellar shell.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ad4da9