Douglas, KM orcid.org/0000-0002-3281-3685, Gobrecht, D and Plane, JMC orcid.org/0000-0003-3648-6893 (2022) Experimental study of the removal of excited state phosphorus atoms by H2O and H2: implications for the formation of PO in stellar winds. Monthly Notices of the Royal Astronomical Society, 515 (1). pp. 99-109. ISSN 0035-8711
Abstract
The reactions of the low-lying metastable states of atomic phosphorus, P(2D) and P(2P), with H2O and H2 were studied by the pulsed laser photolysis at 248 nm of PCl3, combined with laser-induced fluorescence detection of P(2D), P(2P), and PO. Rate coefficients between 291 and 740 K were measured, along with a yield for the production of PO from P(2D or 2P) + H2O of (35 ± 15) %. H2 reacts with both excited P states relatively efficiently; physical (i.e. collisional) quenching, rather than chemical reaction to produced PH + H, is shown to be the more likely pathway. A comprehensive phosphorus chemistry network is then developed using a combination of electronic structure theory calculations and a Master Equation treatment of reactions taking place over complex potential energy surfaces. The resulting model shows that at the high temperatures within two stellar radii of a MIRA variable AGB star in oxygen-rich conditions, collisional excitation of ground-state P(4S) to P(2D), followed by reaction with H2O, is a significant pathway for producing PO (in addition to the reaction between P(4S) and OH). The model also demonstrates that the PN fractional abundance in a steady (non-pulsating) outflow is underpredicted by about 2 orders of magnitude. However, under shocked conditions where sufficient thermal dissociation of N2 occurs at temperatures above 4000 K, the resulting N atoms convert a substantial fraction of PO into PN.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © The Author(s) 2022. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. |
Keywords: | astrochemistry, molecular data, methods: laboratory, stars: winds, outflows |
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: | 16 Jun 2022 14:27 |
Last Modified: | 07 Aug 2022 18:08 |
Status: | Published |
Publisher: | Oxford University Press |
Identification Number: | 10.1093/mnras/stac1684 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:188033 |