Mangan, TP orcid.org/0000-0001-7053-5594, Douglas, KM orcid.org/0000-0002-3281-3685, Lade, RE orcid.org/0000-0003-1773-5655 et al. (3 more authors) (2021) Kinetic Study of the Reactions of AlO with H2O and H2; Precursors to Stellar Dust Formation. ACS Earth and Space Chemistry, 5 (12). pp. 3385-3395. ISSN 2472-3452
Abstract
AlO is relatively abundant around oxygen-rich Asymptotic Giant Branch (AGB) stars, where it can react with major gas-phase species such as H2 and H2O to form AlOH. These Al-containing species are the likely precursors of refractory alumina nanoparticles, which may provide the nuclei for dust formation. In the present study, the kinetics of these AlO reactions were measured from 295 to 780 K using the pulsed laser photolysis of Al(C5H7O2)3, with time-resolved laser induced fluorescence detection of AlO. The experimental results were interpreted using quantum chemistry calculations and a Master Equation solver for reactions with multiple energy wells. For the recombination reaction AlO + H2O (+ N2) → Al(OH)2, log10(krec,0/cm6 molecule–2 s–1) = −32.9185 + 8.80276 log10(T) – 2.4723(log10(T))2; log10(krec,∞/cm3 molecule–1 s–1) = −19.4686 + 7.62037 log10(T) – 1.47214(log10(T))2; Fc = 0.28 (uncertainty ±13% from 295 to 760 K). For the bimolecular reactions, k(AlO + H2O → AlOH + OH) = (3.89 ± 0.47) × 10–10 exp(−(1295 ± 150)/T) and k(AlO + H2 → AlOH + H) = (5.37 ± 0.52) × 10–13 (T/300)(2.77 ± 0.19) exp(−(2190 ± 110)/T) cm3 molecule–1 s–1. Rate coefficients for Al + H2O → AlOH + H, AlOH + H → AlO + H2 or Al + H2O, and the absorption cross sections of AlOH and AlO were calculated theoretically. Al chemistry around an O-rich AGB star was then investigated using a β-trajectory model, which predicts that AlOH is the major gas-phase Al species beyond two stellar radii and shows that the relative AlO abundance is very sensitive to the AlOH photolysis rate.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2021 American Chemical Society. This is an author produced version of an article published in ACS Earth and Space Chemistry. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | AGB stars; alumina dust formation; aluminum oxide reactions; electronic structure theory; laser-based kinetic technique; master equation analysis; RRKM theory; stellar outflow chemistry |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Physical Chemistry (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 25 Oct 2021 13:25 |
Last Modified: | 15 Nov 2022 01:13 |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/acsearthspacechem.1c00225 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:179425 |