Photochemistry of acids and bases at the air - ice interface
Abstract
The dissociation and photochemistry of nitric acid and nitrous acid at ice - air interfaces has since long attracted scientific interest, most notably due to the pivotal role that this surface chemistry plays in modifying the nitrogen oxide budget and thus the oxidative capacity of the atmosphere. A striking enhancement of HNO3 photolysis rates at surfaces is generally attributed to differences in the solvation and hydrogen bonding of nitrate at the surface compared to in the bulk. This is directly related to the liquid-like layer (LLL) for ice surfaces. As temperature approaches the melting point of ice, the hydrogen bonding network at the air - ice interface evolves towards more randomly spatialized interactions [1] .
Flow tube experiments are combined with near ambient pressure core level X-ray photoelectron spectroscopy (XPS) in order to study the interfacial acid-base chemistry and photochemistry on ice [2, 3] . While the flow tube experiments focus on the kinetics and product yields of the different acid-base reactions, XPS work aims to gain information about the surface concentration of the chemical species on ice. The QLL is investigated using Near Edge X-ray Absorption Fine Structure (NEXAFS), aiming to resolve the thickness of clean ice depending on the temperature. We will present a first data set of flow tube experiments, as well as XPS acquired at the NAPP endstation at the Swiss Light Source of the Paul Scherrer Institute of the nitrate adsorbed on ice. These results will be related to earlier work that show how the presence of acid induces changes to the hydrogen bonding network in the interfacial region with impact on photochemistry [2, 3] . The results on this study might also be relevant to the general chemistry as material science and catalysis. Literature References: Grannas, A.M., et al., An overview of snow photochemistry: evidence, mechanisms and impacts. Atmos. Chem. Phys., 2007. 7(16): p. 4329-4373. Křepelová, A., et al., Adsorption of Acetic Acid on Ice Studied by Ambient-Pressure XPS and Partial-Electron-Yield NEXAFS Spectroscopy at 230-240 K. The Journal of Physical Chemistry A, 2013. 117(2): p. 401-409. Kong, X., et al., Coexistence of Physisorbed and Solvated HCl at Warm Ice Surfaces. The Journal of Physical Chemistry Letters, 2017. 8(19): p. 4757-4762. Acknowledgement: SNF for funding (grant 178962)- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A43Q3128M
- Keywords:
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- 0317 Chemical kinetic and photochemical properties;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0340 Middle atmosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0394 Instruments and techniques;
- ATMOSPHERIC COMPOSITION AND STRUCTURE