title: Sulphur Kβ emission spectra reveal protonation states of aqueous sulfuric acid.
abstract: In this paper we report an X-ray emission study of bulk aqueous sulfuric acid. Throughout the range of molarities from 1 M to 18 M the sulfur Kβ emission spectra from H2SO4 (aq) depend on the molar fractions and related deprotonation of H2SO4. We compare the experimental results with results from emission spectrum calculations based on atomic structures of single molecules and structures from ab initio molecular dynamics simulations. We show that the S Kβ emission spectrum is a sensitive probe of the protonation state of the acid molecules. Using non-negative matrix factorization we are able to extract the fractions of different protonation states in the spectra, and the results are in good agreement with the simulation for the higher part of the concentration range.
authors.affiliation: University of Helsinki, Department of Physics, Helsinki, FI-00014, Finland.
authors.forename: Johannes
authors.initials: J
authors.lastname: Niskanen
authors.affiliation: European Synchrotron Radiation Facility, ESRF, Grenoble, France.|University of Helsinki, Department of Physics, Helsinki, FI-00014, Finland.
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Sahle
authors.affiliation: University of Helsinki, Department of Physics, Helsinki, FI-00014, Finland.
authors.forename: Kari O
authors.initials: KO
authors.lastname: Ruotsalainen
authors.affiliation: European Synchrotron Radiation Facility, ESRF, Grenoble, France.
authors.forename: Harald
authors.initials: H
authors.lastname: Müller
authors.affiliation: Jožef Stefan Institute, Jamova cesta 39, SI-1001 Ljubljana, Slovenia.
authors.forename: Matjaž
authors.initials: M
authors.lastname: Kavčič
authors.affiliation: Jožef Stefan Institute, Jamova cesta 39, SI-1001 Ljubljana, Slovenia.|Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, Ljubljana, Slovenia.
authors.forename: Matjaž
authors.initials: M
authors.lastname: Žitnik
authors.affiliation: Jožef Stefan Institute, Jamova cesta 39, SI-1001 Ljubljana, Slovenia.
authors.forename: Klemen
authors.initials: K
authors.lastname: Bučar
authors.affiliation: Jožef Stefan Institute, Jamova cesta 39, SI-1001 Ljubljana, Slovenia.
authors.forename: Marko
authors.initials: M
authors.lastname: Petric
authors.affiliation: University of Helsinki, Department of Physics, Helsinki, FI-00014, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Hakala
authors.affiliation: University of Helsinki, Department of Physics, Helsinki, FI-00014, Finland.
authors.forename: Simo
authors.initials: S
authors.lastname: Huotari