uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
Photoelectron spectroscopy of liquid water and aqueous solution: Electron effective attenuation lengths and emission-angle anisotropy
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Show others and affiliations
2010 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, Vol. 177, no 2-3, 60-70 p.Article in journal (Refereed) Published
Abstract [en]

Photoelectron (PE) spectroscopy measurements from liquid water and from a 4m NaI aqueous solution are performed using a liquid microjet in combination with soft X-ray synchrotron radiation. From the oxygen is PE signal intensity from liquid water, measured as a function of photon energy (up to 1500 eV), we quantitatively determine relative electron inelastic effective attenuation lengths (EAL) for (photo)electron kinetic energies in the 70-900 eV range. In order to determine the absolute electron escape depths a calibration point is needed, which is not directly accessible by experiment. This information can instead be indirectly derived by comparing PE experiments and molecular dynamics (MD) simulations of an aqueous solution interface where density profiles of water, anions, and cations are distinctively different. We have chosen sodium iodide in water because iodide has a considerable propensity for the solution surface, whereas the sodium cation is repelled from the surface. By measuring the intensities of photoelectrons emitted from different orbitals of different symmetries from each aqueous ion we also evaluate whether gas-phase ionization cross sections and asymmetry parameters can describe the photoemission from ions at and near the aqueous solution/vapor interface. We show that gas-phase data reproduce surprisingly well the experimental observations for hydrated ions as long as the photon energy is sufficiently far above the ionization threshold. Electrons detected at the higher photon energies originate predominantly from deeper layers, suggesting that bulk-solution electron elastic scattering is relatively weak.

Place, publisher, year, edition, pages
2010. Vol. 177, no 2-3, 60-70 p.
Keyword [en]
Liquid water and aqueous solutions, X-ray photoelectron spectroscopy, Solution interfacial structure, Electron inelastic mean free path, Electron attenuation lengths in water, Molecular dynamics
National Category
Physical Sciences Chemical Sciences
URN: urn:nbn:se:uu:diva-136438DOI: 10.1016/j.elspec.2009.08.007ISI: 000277949100002OAI: oai:DiVA.org:uu-136438DiVA: diva2:376949
Available from: 2010-12-13 Created: 2010-12-13 Last updated: 2011-07-01Bibliographically approved
In thesis
1. Aqueous Solutions as seen through an Electron Spectrometer: Surface Structure, Hydration Motifs and Ultrafast Charge Delocalization Dynamics
Open this publication in new window or tab >>Aqueous Solutions as seen through an Electron Spectrometer: Surface Structure, Hydration Motifs and Ultrafast Charge Delocalization Dynamics
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In spite of their high abundance and importance, aqueous systems are enigmatic on the microscopic scale. In order to obtain information about their geometrical and electronic structure, simple aqueous solutions have been studied experimentally by photo- and Auger electron spectroscopy using the novel liquid micro-jet technique in conjunction with synchrotron radiation. The thesis is thematically divided into three parts.

In the first part we utilize the surface sensitivity of photoelectron spectroscopy to probe the distributions of solutes near the water surface. In agreement with recent theoretical predictions we find that large polarizable anions, such as I- and ClO4-, display enhanced surface propensities compared to smaller rigid ions. Surface effects arising from ion-ion interactions at higher electrolyte concentrations and as function of pH are investigated. Studies of linear mono-carboxylic acids and benzoic acid show that the neutral molecular forms of such weak acids are better stabilized at the water surface than their respective conjugate base forms.

The second part examines what type of information core-electron spectra can yield about the chemical state and hydration structure of small organic molecules in water. We demonstrate that the method is sensitive to the protonation state of titratable functional groups and that core-level lineshapes are dependent on local water hydration configurations. Using a combination of photoelectron and X-ray absorption spectroscopy we also show that the electronic re-arrangement upon hydrolysis of aldehydes yields characteristic fingerprints in core-level spectra.

In the last part of this thesis we study ultrafast charge delocalization dynamics in aqueous solutions using resonant and off-resonant Auger spectroscopy. Intermolecular Coulombic decay (ICD) is found to occur in a number of core-excited solutions where excess energy is transferred between the solvent and the solute. The rate of ultrafast electron delocalization between hydrogen bonded water molecules upon oxygen 1s resonant core-excitation is found to decrease upon solvation of inorganic ions.

The presented work is illustrative of how core-level photoelectron spectroscopy can be valuable in the study of fundamental phenomena in aqueous solutions.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 118 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 828
Water, Aqueous solutions, Ions, Molecular Hydration, Electron dynamics, Atmospheric Chemistry, Hydrolysis, Acid-Base Chemistry, Interatomic Coulombic Decay, ICD, Liquid Micro-Jet, X-ray Photoelectron Spectroscopy, XPS, Auger Electron Spectroscopy, AES, MAX-lab, BESSY
National Category
Physical Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
urn:nbn:se:uu:diva-151435 (URN)978-91-554-8083-7 (ISBN)
Public defence
2011-06-01, Polhemssalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Available from: 2011-05-11 Created: 2011-04-11 Last updated: 2011-07-01Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text
By organisation
Department of Physics and Astronomy
In the same journal
Journal of Electron Spectroscopy and Related Phenomena
Physical SciencesChemical Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 205 hits
ReferencesLink to record
Permanent link

Direct link