{"title":"Balance of Unimolecular and Bimolecular Pathways Control the Temperature-Dependent Kinetics of Ozonolysis in Aerosols.","authors":"Ryan S Reynolds, Kevin R Wilson","doi":"10.1021/acs.jpca.4c06885","DOIUrl":null,"url":null,"abstract":"<p><p>To better understand the key kinetic mechanisms controlling heterogeneous oxidation in organic aerosols, submicron particles composed of an alkene and a saturated carboxylic acid are exposed to ozone in a variable-temperature flow tube reactor. Effective uptake coefficients (γ<sub>eff</sub>) are obtained from the multiphase reaction kinetics, which are quantified by Vacuum Ultraviolet Photoionization Aerosol Mass Spectrometry. For aerosols composed of only of alkenes, γ<sub>eff</sub> doubles (from 6 × 10<sup>-4</sup> to 1.2 × 10<sup>-3</sup>) when the temperature is decreased from 293 to 263 K. Alternatively, for an alkene particle doped with a carboxylic acid, an efficient scavenger of stabilized Criegee Intermediates (sCI), γ<sub>eff</sub> is observed to be weakly temperature dependent. A kinetic model, benchmarked to literature data, explains these results as arising from the temperature dependent competition between unimolecular pathways of sCI that promote radical chain cycling and those bimolecular pathways that form stable chain termination products (i.e., α-acyloxyalkyl hydroperoxides). The implication of these results for the kinetics of aerosol aging at low temperatures is discussed.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7000,"publicationDate":"2024-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"The Journal of Physical Chemistry A","FirstCategoryId":"1","ListUrlMain":"https://doi.org/10.1021/acs.jpca.4c06885","RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
Abstract
To better understand the key kinetic mechanisms controlling heterogeneous oxidation in organic aerosols, submicron particles composed of an alkene and a saturated carboxylic acid are exposed to ozone in a variable-temperature flow tube reactor. Effective uptake coefficients (γeff) are obtained from the multiphase reaction kinetics, which are quantified by Vacuum Ultraviolet Photoionization Aerosol Mass Spectrometry. For aerosols composed of only of alkenes, γeff doubles (from 6 × 10-4 to 1.2 × 10-3) when the temperature is decreased from 293 to 263 K. Alternatively, for an alkene particle doped with a carboxylic acid, an efficient scavenger of stabilized Criegee Intermediates (sCI), γeff is observed to be weakly temperature dependent. A kinetic model, benchmarked to literature data, explains these results as arising from the temperature dependent competition between unimolecular pathways of sCI that promote radical chain cycling and those bimolecular pathways that form stable chain termination products (i.e., α-acyloxyalkyl hydroperoxides). The implication of these results for the kinetics of aerosol aging at low temperatures is discussed.
期刊介绍:
The Journal of Physical Chemistry A is devoted to reporting new and original experimental and theoretical basic research of interest to physical chemists, biophysical chemists, and chemical physicists.