The role of surface molecular hydrates in the heterogeneous interaction of NH3 with sulfuric acid monohydrate

Karen L. Nash, Robert M. Sayer, Suzanne B. Couling, John Fletcher, Alex Henderson, John C. Vickerman, Andrew B. Horn

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The interaction of gaseous NH3 with thin films of sulfuric acid monohydrate (SAM, H3O+HSO4-) in the 200-230 K range has been monitored by infrared spectroscopy and secondary ion mass spectrometry. The reaction occurs with the formation of the characteristic IR spectral features of the NH4+ and "salt" bisulfate ions, whilst loss of H3O+ and an additional surface species is observed. The evolution of the spectral features with time suggest that two processes are occurring at the uppermost surface layers, with a rapid initial reaction which saturates as the amount of available reactants on the surface is reduced and a slower continuous process which depends upon the transport of new reactants to and the removal of reaction products away from the surface. By comparison with the IR spectra of a variety of sulfuric acid hydrates, a surface reaction scheme is proposed and the implications of these observations for the reaction of condensed acids (sulfate aerosol) with bases in the atmosphere is discussed.
    Original languageEnglish
    Pages (from-to)5101-5107
    Number of pages6
    JournalPhysical Chemistry Chemical Physics
    Volume5
    Issue number22
    DOIs
    Publication statusPublished - 15 Nov 2003

    Keywords

    • Surface reaction (mol. hydrate effects in heterogeneous interaction of gaseous ammonia with thin films of sulfuric acid monohydrate)
    • Atmospheric aerosols (surface mol. hydrate effects in heterogeneous interaction of gaseous ammonia with thin films of sulfuric acid monohydrate)
    • surface mol hydrate heterogeneous interaction ammonia sulfuric acid monohydrate

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