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Solvent–Solute Interaction: Studied by Synchrotron Radiation Based Photo and Auger Electron Spectroscopies
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Aqueous solutions were studied using photoelectron and Auger spectroscopy, based on synchrotron radiation and a liquid micro-jet setup.

By varying the photon energy in photoelectron spectra, we depth profiled an aqueous tetrabutylammonium iodide (TBAI) solution. Assuming uniform angular emission from the core levels, we found that the TBA+ ions were oriented at the surface with the hydrophobic butyl arms sticking into the liquid.

We investigated the association between ions and their neighbors in aqueous solutions by studying the electronic decay after core ionization. The (2p)−1 decay of solvated K+ and Ca2+ ions was studied. The main features in the investigated decay spectra corresponded to two-hole final states localized on the ions. The spectra also showed additional features, related to delocalized two-hole final states with vacancies on a cation and a neighboring water molecule. These two processes compete, and by comparing relative intensities and using the known rate for the localized decay, we determined the time-scale for the delocalized process for the two ions. We compared to delocalized electronic decay processes in Na+, Mg2+, and Al3+, and found that they were slower in K+ and Ca2+, due to different internal decay mechanisms of the ions, as well as external differences in the ion-solute distances and interactions.

In the O 1s Auger spectra of aqueous metal halide solutions, we observed features related to delocalized two-hole final states with vacancies on a water molecule and a neighboring solvated anion. The relative intensity of these feature indicated that the strength of the interaction between the halide ions and water correlated with ionic size.

The delocalized decay was also used to investigate contact ion pair formation in high concentrated potassium halide solutions, but no concrete evidence of contact ion pairs was observed.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2011. , p. 73
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 796
Keywords [en]
Interatomic Coulombic Decay, ICD, Auger electron spectroscopy, AES, X-ray photoelectron spectroscopy, XPS, Ultra-violet spectroscopy, UPS, localized, delocalized, double ionization potential, DIP, two hole, final states, Water, H2O, Potassium chloride, KCl, Calcium chloride, CaCl2, Ammonium, NH4, Core hole, clock, lifetime, solvated, ion, alkali, halide, Coster Kronig, MAX-lab, BESSY
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-138749ISBN: 978-91-554-7980-0 (print)OAI: oai:DiVA.org:uu-138749DiVA, id: diva2:379733
Public defence
2011-02-04, Häggsalen, Ångström laboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Note
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 726Available from: 2011-01-14 Created: 2010-12-19 Last updated: 2011-03-21Bibliographically approved
List of papers
1. A photoelectron spectroscopic study of aqueous tetrabutylammonium iodide
Open this publication in new window or tab >>A photoelectron spectroscopic study of aqueous tetrabutylammonium iodide
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2007 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 19, no 32, p. 326101-Article in journal (Refereed) Published
Abstract [en]

Photoelectron spectra of tetrabutylammonium iodide (TBAI) dissolved in water have been recorded using a novel experimental set-up, which enables photoelectron spectroscopy of volatile liquids. The set-up is described in detail. Ionization energies are reported for I 5p, I 4d, C 1s and N 1s. The C 1s spectrum shows evidence of inelastic scattering of the photoelectrons, that differs from the case of TBAI in formamide.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-97066 (URN)10.1088/0953-8984/19/32/326101 (DOI)000248185800005 ()
Available from: 2008-04-18 Created: 2008-04-18 Last updated: 2017-12-14
2. Charge delocalization dynamics of ammonia in different hydrogen bonding environments: free clusters and in liquid water solution
Open this publication in new window or tab >>Charge delocalization dynamics of ammonia in different hydrogen bonding environments: free clusters and in liquid water solution
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2009 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 11, no 11, p. 1758-1764Article in journal (Refereed) Published
Abstract [en]

Valence and core level photoelectron spectra and Auger electron spectra of ammonia in pure clusters have been measured. The Auger electro  spectra of gas-phase ammonia, pure ammonia clusters and ammonia in   aqueous solution are compared and interpreted via ab initio calculations of the Auger spectrum of the ammonia monomer and dimer. The calculations reveal that the final two-hole valence states can be   delocalized over both ammonia molecules. Features at energies   pertaining to delocalized states involving one, or more, hydroge  bonding orbitals can be found in both the ammonia cluster Auger   electron spectrum and in that of the liquid solvated molecule. The lower Coulombic repulsion between two delocalized valence final state holes gives higher kinetic energy of the Auger electrons which is also   observed in the spectra. This decay path-specific to the condensed   phase-is responsible for more than 5% of the total cluster Auger intensity. Moreover, this interpretation is also applicable to the   solid phase since the same features have been observed, but not assigned, in the Auger spectrum of solid ammonia.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-96757 (URN)10.1039/b815657c (DOI)000263838200012 ()
Available from: 2008-02-28 Created: 2008-02-28 Last updated: 2017-12-14Bibliographically approved
3. Auger electron spectroscopy as a probe of the solution of aqueous ions
Open this publication in new window or tab >>Auger electron spectroscopy as a probe of the solution of aqueous ions
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2009 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, no 21, p. 7264-7271Article in journal (Refereed) Published
Abstract [en]

Aqueous potassium chloride has been studied by synchrotron-radiation   excited core-level photoelectron and Auger electron spectroscopy. In   the Auger spectrum of the potassium ion, the main feature comprises the final states where two outer valence holes are localized on potassium. This spectrum exhibits also another feature at a higher kinetic energy   which is related to final states where outer valence holes reside on different subunits. Through ab initio calculations for microsolvated clusters, these subunits have been assigned as potassium ions and the surrounding water molecules. The situation is more complicated in the Auger spectrum of the chloride anion. One-center and multicenter final states are present here as well but overlap energetically.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-97067 (URN)10.1021/ja8096866 (DOI)000266484900025 ()
Available from: 2008-04-18 Created: 2008-04-18 Last updated: 2017-12-14Bibliographically approved
4. Charge Dependence of Solvent-Mediated Intermolecular Coster-Kronig Decay Dynamics of Aqueous Ions
Open this publication in new window or tab >>Charge Dependence of Solvent-Mediated Intermolecular Coster-Kronig Decay Dynamics of Aqueous Ions
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2010 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 51, p. 17057-17061Article in journal (Refereed) Published
Abstract [en]

The 2s and 2p photoelectron spectra have been measured for Na+, Mg2+, and Al3+ ions in aqueous solution.In all cases, the 2s lines are significantly broader than the 2p features, which is attributed to a shorter lifetimeof the respective 2s hole. Since intraionic Coster-Kronig decay channels from the (2s)-1 state are closed forfree Na+, Mg2+, and Al3+ ions, this is evidence for an intermolecular Coster-Kronig-like process, reminiscentof intermolecular Coulombic decay (ICD), involving neighboring water solvent molecules. The observed 2s Lorentzian line widths correspond to lifetimes of the (2s)-1 state of 3.1, 1.5, and 0.98 fs for the solvated Na,Mg, and Al ions, respectively.

National Category
Physical Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-138741 (URN)10.1021/jp108956v (DOI)000285560100006 ()
Available from: 2010-12-19 Created: 2010-12-19 Last updated: 2017-12-11Bibliographically approved
5. Ionic charge dependence of ion-solvent ICD time-scale for aqueous ions probed by the core-hole clock
Open this publication in new window or tab >>Ionic charge dependence of ion-solvent ICD time-scale for aqueous ions probed by the core-hole clock
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Auger electron spectroscopy combined with theoretical calculations have been applied to investigate the decay of the Ca 2p core hole of aqueous Ca2+. Localized final states due to Auger-like and de-localized final states due to ICD-like decay processes are identified. By applying the core-hole clock spectroscopy method, the time constant of the ICD-like decay was determined to 24±6 fs for Ca2+. We have compared to ICD-like processes in other aqueous ions, K+, Na+, Mg2+ and Al3+, and observe a variation of the time constants of two orders of magnitude. This large variation is qualitatively explained by differences both internal and external to the ions; different internal decay mechanisms of the ions, as well as external differences in the ion-solute distances and interactions.

National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-138742 (URN)
Available from: 2010-12-19 Created: 2010-12-19 Last updated: 2011-04-11
6. Bond Breaking, Electron Pushing and Proton Pulling: Active and Passive Roles in the Interaction between Aqueous Ions and Water as Manifested in the O 1s Auger Decay
Open this publication in new window or tab >>Bond Breaking, Electron Pushing and Proton Pulling: Active and Passive Roles in the Interaction between Aqueous Ions and Water as Manifested in the O 1s Auger Decay
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2012 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 116, no 1, p. 3-8Article in journal (Refereed) Published
Abstract [en]

A core-ionized H2O molecule in liquid water primarily relaxes through normal Auger decay, leading to a two-hole final state in which both valence holes are localized on the same water molecule. Electronic coupling to the environment, however, allows for alternative decays resembling Intermolecular Coulombic Decay (ICD), producing final states with one of the holes delocalized on a neighboring water molecule. Here we present an experimental study of such minority processes, which adds to our understanding of dynamic interactions of electronically excited H2O molecules with their local surrounding in liquid water and aqueous solution. We show that the solvation of metal-halide salts considerably influences these minority decay channels from the water 0 1s-1 state. By breaking water-water bonds, both the metal cations and halide anions are found to reduce the decay into water-water delocalized states, thus having a "passive" effect on the Auger spectrum. The halide anions also play an "active" role by opening a new ICD-like decay pathway into water-halide delocalized states. The importance of this contribution increases from F- to I-, which we suggest to be caused by a directional polarization of the halide anion toward the core-ionized H2O+ cation in the intermediate state of the Auger process. This increases the electronic overlap between the two centers and makes delocalized decays more probable. We furthermore show that F-, the smallest and most strongly hydrated of the halides, plays an additional role as proton puller during the core-hole lifetime, resulting in proton dynamics on the low femtosecond time scale. Our results represent a step forward toward a better understanding of how aqueous solutions, when exposed to soft X-rays, channel excess energy. This has implications for several aspects of physical and radiation chemistry, as well as biology.

National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-138743 (URN)10.1021/jp2041247 (DOI)000298978100002 ()
Available from: 2010-12-19 Created: 2010-12-19 Last updated: 2017-12-11Bibliographically approved
7. No signature of contact ion pairs in the K 2p Auger spectra of highlyconcentrated potassium halide solutions
Open this publication in new window or tab >>No signature of contact ion pairs in the K 2p Auger spectra of highlyconcentrated potassium halide solutions
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2014 (English)In: ScienceAsia, ISSN 1513-1874, Vol. 40, no 4, p. 290-294Article in journal (Refereed) Published
Abstract [en]

Possible ion pair formation in highly concentrated aqueous potassium halide solutions (fluoride,chloride, and bromide) has been investigated by applied Auger electron spectroscopy. The potassiumAuger spectra exhibit features at high kinetic energy, which are related to final states withvacancies on the potassium ion and a neighboring water molecule. The potassium ion could possiblyassociate with a halide ion as well, giving rise to additional final states with a vacancy onthe halide instead of a water molecule which should give rise to separable spectral features. Thenecessity of close proximity of the ions for such decays to occur would be strong evidence thatcontact ions pairs are present in the solution, but no features related to final states involving theanion could be observed in this work.

National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-138744 (URN)10.2306/scienceasia1513-1874.2014.40.290 (DOI)000344436800005 ()
Available from: 2010-12-19 Created: 2010-12-19 Last updated: 2017-12-11Bibliographically approved

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  • nn-NB
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Output format
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