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Charge delocalization dynamics of ammonia in different hydrogen bonding environments: free clusters and in liquid water solution
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
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2009 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 11, no 11, 1758-1764 p.Article 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.

Place, publisher, year, edition, pages
2009. Vol. 11, no 11, 1758-1764 p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-96757DOI: 10.1039/b815657cISI: 000263838200012OAI: oai:DiVA.org:uu-96757DiVA: diva2:171436
Available from: 2008-02-28 Created: 2008-02-28 Last updated: 2017-12-14Bibliographically approved
In thesis
1. A Treatise on the Geometric and Electronic Structure of Clusters: Investigated by Synchrotron Radiation Based Electron Spectroscopies
Open this publication in new window or tab >>A Treatise on the Geometric and Electronic Structure of Clusters: Investigated by Synchrotron Radiation Based Electron Spectroscopies
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Clusters are finite ensembles of atoms or molecules with sizes in the nanometer regime (i.e. nanoparticles). This thesis present results on the geometric and electronic structure of homogeneous and heterogeneous combinations of atoms and molecules. The systems have been studied with synchrotron radiation and valence, core and Auger electron spectroscopic techniques.

The first theme of the thesis is that of mixed clusters. It is shown that by varying the cluster production technique both structures that are close to that predicted by equilibrium considerations can be attained as well as far from equilibrium structures.

Electronic processes following ionization constitute the second theme. The post-collision interaction phenomenon, energy exchange between the photo- and the Auger electrons, is shown to be different in clusters of argon, krypton and xenon. A model is proposed that takes polarization screening in the final state into account. This result is of general character and should be applicable to the analysis of core level photoelectron and Auger electron spectra of insulating and semi-conducting bulk materials as well.

Interatomic Coloumbic Decay is a process that can occur in the condensed phases of weakly bonded systems. Results on the time-scale of the process in Ne clusters and mixed Ar/Ne clusters are herein discussed, as well observations of resonant contributions to the process. In analogy to Auger vis-à-vis Resonant Auger it is found that to the ICD process there is a corresponding Resonant ICD process possible. This has later been observed in other systems and by theoretical calculations as well in subsequent works by other groups.

Delocalization of dicationic valence final states in the hydrogen bonded ammonia clusters and aqueous ammonia has also been investigated by Auger electron spectroscopy. With those results it was possible to assign a previously observed feature in the Auger electron spectrum of solid ammonia.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 103 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 393
Keyword
Cluster, nanoparticle, Heterogeneous, Homogeneous, Mixed, Cluster production methods, co-expansion, pick-up, doping, Cluster geometry, radial segregation, Interatomic Coulombic Decay, ICD, Auger electron spectroscopy, AES, X-ray photoelectron spectroscopy, XPS, Ultra-violet spectroscopy, UPS, Noble gas, Rare gas, Ne, Ar, Kr, Xe, Ammonia, NH3, Sulphur hexafluoride, SF6, MAX-lab, BESSY
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-8463 (URN)978-91-554-7095-1 (ISBN)
Public defence
2008-03-14, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15
Opponent
Supervisors
Available from: 2008-02-28 Created: 2008-02-28Bibliographically approved
2. Solvent–Solute Interaction: Studied by Synchrotron Radiation Based Photo and Auger Electron Spectroscopies
Open this publication in new window or tab >>Solvent–Solute Interaction: Studied by Synchrotron Radiation Based Photo and Auger Electron Spectroscopies
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. 73 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 796
Keyword
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:nbn:se:uu:diva-138749 (URN)978-91-554-7980-0 (ISBN)
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

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