Experimental studies of the structural, dynamical and electronic properties of clusters and nanoparticles

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

IT116

Topic of the dissertation

Experimental studies of the structural, dynamical and electronic properties of clusters and nanoparticles

Doctoral candidate

Master of Science Eetu Pelimanni

Faculty and unit

University of Oulu Graduate School, Faculty of Science, Nano and Molecular Systems Research Unit (NANOMO)

Subject of study

Physics

Opponent

Docent Michal Fárník, J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Prague, Czech Republic

Custos

Assoc. Prof. (Tenure track) Minna Patanen, Oulun yliopisto

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Experimental studies of the structural, dynamical and electronic properties of clusters and nanoparticles

Water plays a fundamental role in the world that we live in. In the oceans, the atmosphere and all living things, countless numbers of water molecules are interacting with each other and with other atoms and molecules. A thorough understanding of these interactions can only be achieved by studying the electronic properties and molecular level physical phenomena that occur in aqueous systems.

This dissertation focuses on nanometer sized water droplets, i.e. water clusters, and particularly on the electronic properties and behavior of inorganic species in them. The properties of nanoscopic systems are often unique, and their investigation also improves understanding of how the properties of macroscopic solutions evolve from the collective effects of solutes and water molecules.

The experiments were carried out in international synchrotron radiation laboratories SOLEIL in France and MAX IV in Sweden, as well as in the University of Oulu. The samples were irradiated with ionizing radiation, and information was obtained by analyzing the correspondingly emitted electrons and ions.

In the first part of this work, the properties and surface enrichment of alkali, alkaline earth and halide ions were investigated in 100–200 nanometer sized nanoparticles. The results revealed for example significant enrichment of magnesium in the surface of particles generated from aqueous sodium bromide-magnesium bromide solutions. The results lead to better understanding of the structural properties of aerosol particles generated from aqueous solutions, and thereby increase knowledge also on the surface properties of natural sea spray aerosols.

In the second part of this work, the electronic properties of potassium chloride solvated in 2–3 nanometer sized water clusters were examined. The core and valence level energetics were probed as a function of cluster size and salt concentration. The results aid in bridging the gap between atomic physics and the physics of condensed aqueous solutions.

In the third part of this work, the interaction of high energy electrons with hydrated atoms was investigated in argon-water heteroclusters. By application of an electron-ion multicoincidence detection technique, a particular inner shell ionization process could be selectively monitored. The results revealed for example that upon double ionization of an argon atom, water molecules will efficiently donate electrons to the original ionization site before the cluster dissociates. The results provide qualitative understanding of inner shell ionization processes and radiolytic effects in clusters and in aqueous environments in general.
Last updated: 30.5.2022