AlOSO: Spectroscopy and Structure of a New Group of Astrochemical Molecules

With the ever-increasing detection of sulfur-bearing molecules and the high abundance and refractory nature of aluminum, the [Al, S, O 2 ] isomers may play an important role in the gas-phase chemistry of circumstellar envelopes and the chemistry on the surface of dust grains. High-level theoretical...

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Bibliographic Details
Published in:The Astrophysical journal 2022-05, Vol.930 (1), p.29
Main Authors: Esposito, Vincent J., Trabelsi, Tarek, Francisco, Joseph S.
Format: Article
Language:English
Subjects:
Absorption spectra
Aluminum
Astrochemistry
Astrophysics
Asymptotes
Circumstellar envelopes
Computational methods
Cosmic dust
Diamonds
Dipole moments
Dissociation
Interstellar medium
Isomers
Molecular spectroscopy
Rotational spectra
Spectroscopy
Stellar envelopes
Sulfur
Sulfur dioxide
Vibrational spectra
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Summary:With the ever-increasing detection of sulfur-bearing molecules and the high abundance and refractory nature of aluminum, the [Al, S, O 2 ] isomers may play an important role in the gas-phase chemistry of circumstellar envelopes and the chemistry on the surface of dust grains. High-level theoretical exploration of the [Al, S, O 2 ] molecular system yielded five isomers, and predictions of their rotational, vibrational, and electronic spectroscopic properties are provided to inform experimental and observational searches. Cis-AlOSO and diamond isomers are isoenergetic and connected via a very small (∼1 kcal mol −1 ) transition-state barrier. These isomers may act as intermediates along the chemical pathway between Al + SO 2 and AlO + SO. Other isomers OAlOS and SAlO 2 are stable relative to their corresponding dissociation asymptotes. Large permanent dipole moments of 2.521 D (cis-AlOSO), 1.239 D (diamond), and 5.401 D (OAlOS) predict strong rotational transitions and indicate these molecules as prime candidates for experimental study. Due to the low transition-state barrier, mixing of the vibrational levels is anticipated, complicating the vibrational spectrum. Electronic spectroscopy may be used as a means to differentiate between the two isomers. Strong electronic transitions are predicted to occur in the 200–300 nm range for cis-AlOSO and diamond. Simulated electronic absorption spectra provide a starting point for experimental characterization and spectral deconvolution of these isomers.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ac6178