Postgraduate Seminar: Maggie Corrigan
Wednesday, 21 October 2020. 11am – 12pm.
This seminar will be delivered via Zoom – Please email chemistry.researchsupport@sydney.edu.au for zoom link and password.
Maggie Corrigan, PhD Candidate, School of Chemistry.
Host: Prof Meredith Jordan
Abstract: OH and HO2 radicals are important tropospheric oxidants, breaking down the volatile organic compounds emitted by plants and human activity [1]. Measurement and modelling of these species in the troposphere are inconsistent: in particular, OH concentration is often underestimated by an order of magnitude in remote areas [2]. This suggests a missing source of OH in tropospheric chemistry models. OH and HO2 concentrations in the troposphere, however, are interlinked, as each often react to form the other [3]. Therefore, a previously unknown source of HO2 in the troposphere could be responsible for this discrepancy between model and measurement.
Experimental evidence in the group [4] suggests that highly vibrationally excited ground state H2CO (produced following photoexcitation and non-radiative relaxation back to the ground state) can react directly with O2 under tropospheric conditions to produce HO2. This reaction is referred to as an atmospheric photothermal oxidation reaction, or APTO. Subsequent computational analysis in this work confirmed the energetic accessibility of such a reaction. As there are several carbonyl-containing species in the troposphere, APTO could be critical to explaining measurement and modelling inconsistencies.
In this talk I will present computational work that suggests this APTO reaction is energetically accessible for a wide range of carbonyl-containing species, and their isomers, including enols, ketenes and oxetenes. This reaction is likely to be energetically accessible in the troposphere for a number of species, and will therefore be important in tropospheric modelling.
[1] Finlayson-Pitts, B. J.; Pitts Jr., J. N. Chemistry of the Upper and Lower Atmosphere: Theory, Experiments, and Applications; Academic Press, 2000.
[2] Stone, D.; Whalley, L. K.; Heard, D. E. Chemical Society Reviews 2012, 41, 6348–6404.
[3] Atkinson, R. Atmospheric Environment 2000, 34, 2063–2101.
[4] Welsh, B.; Corrigan, M.; Assaf, E.; Nauta, K.; Jordan, M. J.; Fittschen, C.; Kable, S. H. unpublished.