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Photochemistry of glyoxylate embedded in sodium chloride clusters, a laboratory model for tropospheric sea-salt aerosols
Although marine aerosols undergo extensive photochemical processing in the troposphere, a molecular level understanding of the elementary steps involved in these complex reaction sequences is still missing. As a defined laboratory model system, the photodissociation of sea salt clusters doped with g...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Royal Society of Chemistry
2018
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5885371/ https://www.ncbi.nlm.nih.gov/pubmed/29517776 http://dx.doi.org/10.1039/c8cp00399h |
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author | Bersenkowitsch, Nina K. Ončák, Milan van der Linde, Christian Herburger, Andreas Beyer, Martin K. |
author_facet | Bersenkowitsch, Nina K. Ončák, Milan van der Linde, Christian Herburger, Andreas Beyer, Martin K. |
author_sort | Bersenkowitsch, Nina K. |
collection | PubMed |
description | Although marine aerosols undergo extensive photochemical processing in the troposphere, a molecular level understanding of the elementary steps involved in these complex reaction sequences is still missing. As a defined laboratory model system, the photodissociation of sea salt clusters doped with glyoxylate, [Na(n)Cl(n–2)(C(2)HO(3))](+), n = 5–11, is studied by a combination of mass spectrometry, laser spectroscopy and ab initio calculations. Glyoxylate acts as a chromophore, absorbing light below 400 nm via two absorption bands centered at about 346 and 231 nm. Cluster fragmentation dominates, which corresponds to internal conversion of the excited state energy into vibrational modes of the electronic ground state and subsequent unimolecular dissociation. Photochemical dissociation pathways in electronically excited states include CO and HCO elimination, leading to [Na(n–x)Cl(n–x–2)HCOO](+) and [Na(n)Cl(n–2)COO˙](+) with typical quantum yields in the range of 1–3% and 5–10%, respectively, for n = 5. The latter species contains CO(2)˙(–) stabilized by the salt environment. The comparison of different cluster sizes shows that the fragments containing a carbon dioxide radical anion appear in a broad spectral region of 310–380 nm. This suggests that the elusive CO(2)˙(–) species may be formed by natural processes in the troposphere. Based on the photochemical cross sections obtained here, the photolysis lifetime of glyoxylate in a dry marine aerosol is estimated as 10 h. Quantum chemical calculations show that dissociation along the C–C bond in glyoxylic acid as well as glyoxylate embedded in the salt cluster occurs after reaching the S(1)/S(0) conical intersection, while this conical intersection is absent in free glyoxylate ions. |
format | Online Article Text |
id | pubmed-5885371 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | Royal Society of Chemistry |
record_format | MEDLINE/PubMed |
spelling | pubmed-58853712018-04-19 Photochemistry of glyoxylate embedded in sodium chloride clusters, a laboratory model for tropospheric sea-salt aerosols Bersenkowitsch, Nina K. Ončák, Milan van der Linde, Christian Herburger, Andreas Beyer, Martin K. Phys Chem Chem Phys Chemistry Although marine aerosols undergo extensive photochemical processing in the troposphere, a molecular level understanding of the elementary steps involved in these complex reaction sequences is still missing. As a defined laboratory model system, the photodissociation of sea salt clusters doped with glyoxylate, [Na(n)Cl(n–2)(C(2)HO(3))](+), n = 5–11, is studied by a combination of mass spectrometry, laser spectroscopy and ab initio calculations. Glyoxylate acts as a chromophore, absorbing light below 400 nm via two absorption bands centered at about 346 and 231 nm. Cluster fragmentation dominates, which corresponds to internal conversion of the excited state energy into vibrational modes of the electronic ground state and subsequent unimolecular dissociation. Photochemical dissociation pathways in electronically excited states include CO and HCO elimination, leading to [Na(n–x)Cl(n–x–2)HCOO](+) and [Na(n)Cl(n–2)COO˙](+) with typical quantum yields in the range of 1–3% and 5–10%, respectively, for n = 5. The latter species contains CO(2)˙(–) stabilized by the salt environment. The comparison of different cluster sizes shows that the fragments containing a carbon dioxide radical anion appear in a broad spectral region of 310–380 nm. This suggests that the elusive CO(2)˙(–) species may be formed by natural processes in the troposphere. Based on the photochemical cross sections obtained here, the photolysis lifetime of glyoxylate in a dry marine aerosol is estimated as 10 h. Quantum chemical calculations show that dissociation along the C–C bond in glyoxylic acid as well as glyoxylate embedded in the salt cluster occurs after reaching the S(1)/S(0) conical intersection, while this conical intersection is absent in free glyoxylate ions. Royal Society of Chemistry 2018-03-28 2018-02-28 /pmc/articles/PMC5885371/ /pubmed/29517776 http://dx.doi.org/10.1039/c8cp00399h Text en This journal is © The Royal Society of Chemistry 2018 http://creativecommons.org/licenses/by/3.0/ This article is freely available. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (CC BY 3.0) |
spellingShingle | Chemistry Bersenkowitsch, Nina K. Ončák, Milan van der Linde, Christian Herburger, Andreas Beyer, Martin K. Photochemistry of glyoxylate embedded in sodium chloride clusters, a laboratory model for tropospheric sea-salt aerosols |
title | Photochemistry of glyoxylate embedded in sodium chloride clusters, a laboratory model for tropospheric sea-salt aerosols
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title_full | Photochemistry of glyoxylate embedded in sodium chloride clusters, a laboratory model for tropospheric sea-salt aerosols
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title_fullStr | Photochemistry of glyoxylate embedded in sodium chloride clusters, a laboratory model for tropospheric sea-salt aerosols
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title_full_unstemmed | Photochemistry of glyoxylate embedded in sodium chloride clusters, a laboratory model for tropospheric sea-salt aerosols
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title_short | Photochemistry of glyoxylate embedded in sodium chloride clusters, a laboratory model for tropospheric sea-salt aerosols
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title_sort | photochemistry of glyoxylate embedded in sodium chloride clusters, a laboratory model for tropospheric sea-salt aerosols |
topic | Chemistry |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5885371/ https://www.ncbi.nlm.nih.gov/pubmed/29517776 http://dx.doi.org/10.1039/c8cp00399h |
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