Protonation Dynamics and Hydrogen Bonding in Aqueous Sulfuric Acid.
Hydration of sulfuric acid plays a key role in new-particle formation in the atmosphere. It has been recently proposed that proton dynamics is crucial in the stabilization of these clusters. One key question is how water molecules mediate proton transfer from sulfuric acid, and hence how the deprotonation state of the acid molecule behaves as a function concentration. We address the proton transfer in aqueous sulfuric acid with O K edge and S L edge core-excitation spectra recorded using inelastic X-ray scattering and with ab initio molecular dynamics simulations in the concentration range of 0-18.0 M. Throughout this range, we quantify the acid-water interaction with atomic resolution. Our simulations show that the number of donated hydrogen bonds per Owater increases from 1.9 to 2.5 when concentration increases from 0 to 18.0 M, in agreement with a rapid disappearance of the pre-edge feature in the O K edge spectrum. The simulations also suggest that for 1.5 M sulfuric acid SO4(2-) is most abundant and that its concentration falls monotonously with increasing concentration. Moreover, the fraction of HSO4(-) peaks at ∼12 M.
Department of Physics, University of Helsinki , P.O. Box 64, FI-00014 Helsinki, Finland.
Johannes
J
Niskanen
Department of Physics, University of Helsinki , P.O. Box 64, FI-00014 Helsinki, Finland.|ESRF-The European Synchrotron , CS40220, 38043, Grenoble Cedex 9, France.
Christoph J
CJ
Sahle
Department of Physics, University of Helsinki , P.O. Box 64, FI-00014 Helsinki, Finland.
Iina
I
Juurinen
Department of Physics, University of Helsinki , P.O. Box 64, FI-00014 Helsinki, Finland.
Jaakko
J
Koskelo
Department of Physics, University of Helsinki , P.O. Box 64, FI-00014 Helsinki, Finland.
Susi
S
Lehtola
ESRF-The European Synchrotron , CS40220, 38043, Grenoble Cedex 9, France.
Roberto
R
Verbeni
ESRF-The European Synchrotron , CS40220, 38043, Grenoble Cedex 9, France.
Harald
H
Müller
Department of Physics, University of Helsinki , P.O. Box 64, FI-00014 Helsinki, Finland.
Mikko
M
Hakala
Department of Physics, University of Helsinki , P.O. Box 64, FI-00014 Helsinki, Finland.
Simo
S
Huotari
D006860:Hydrogen Bonding; D056004:Molecular Dynamics Simulation; D011522:Protons; D013057:Spectrum Analysis; D013464:Sulfuric Acids / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
D011522:Protons; D013464:Sulfuric Acids; D014867:Water; C033158:sulfuric acid