Laboratory of electronic structure and laboratory of microtomography

We carried out experimental research using actively synchrotron light sources, most notably the European Synchrotron Radiation Facility (ESRF) and MAX-Lab. Significant results were also obtained with the in-house x-ray scattering and x-ray micro-tomography (µ-CT) equipment. One highlight of the year was time-resolved X-ray Raman spectroscopy study, published in Scientific Reports, revealing a photoinduced topochemical reaction in crystalline cinnamic acid. This work paves the way for other time-resolved studies on chemical reactions by advanced x-ray methods. The study was done in collaboration with the Department of Chemistry and ESRF, and supercomputer resources of CSC.


The µ-CT facility was upgraded with a new automated µ-CT scanner with sub-micrometer resolution (Bruker SkyScan 1272) together with the Institute of Biotechnology and the Faculty of Medicine. We continued collaboration with the Department of Mathematics and the Finnish Center of Excellence in Inverse Problems Research so that a new medium-resolution (50 µm) µ-CT scanner dedicated to inversion problems and student exercises was built to the 3D-imaging facility. A new in-situ tensile testing rig for studies of concrete samples was designed and developed in collaboration with Aalto University. The scientific topics of µ-CT were highly multidisciplinary, including studies on zoology, biomechanics, geology, and construction materials. We offer µ-CT services by compensation to give an easy access for non-experts to high quality 3D imaging and had clients with diverse backgrounds, including high technology industry, art / design and entertainment, as well as fundamental scientific research.

Studies of cellulose and other natural polymer based materials were continued in collaboration with the Department of Chemistry, the Faculty of Pharmacy, and Massachusetts Institute of Technology. The effects of ionic liquids on liposomes and the structures of bacterial S-layer proteins and liposomes were studied using small-angle x-ray scattering in co-operation with the Department of Chemistry and the Department of Veterinary Biosciences. Also the medical synchrotron research group continued physiological studies at the ESRF.

We were highly active in using hard-x-ray inelastic x-ray scattering spectroscopy at ESRF. Topics included the studies of the ionic conductivity in Mg2C60, a material promising for Mg-ion battery technology, as well as its thermal structural stability. We continued our studies of new materials for Li-ion batteries, catalysis reactions in zeolites, as well as exciton dynamics in layered materials (e.g., MoS2 and hexagonal BN). We also developed and utilized novel ways to use x-ray standing waves in x-ray spectroscopy.

Our studies using Computational modeling of the electronic structure and the radiation-matter interaction both in resonant and non-resonant conditions focused on molecular systems, thin-film and emerging photovoltaic materials, intercalation compounds for energy storage and zeolite catalysts. We won the CSC Grand Challenge computational project for analyzing perovskite photovoltaic materials.

Moreover, our continued effort to resolve diverse problems using the principle of least action resulted in several papers. 

The Laboratory organized the Finnish Synchrotron Radiation Users’ workshop in December and one of us acted as the head of the organizing committee of the Finnish Physical Society Annual Meeting, the 49th Physics Days, organized in Helsinki. The Laboratory’s research was widely presented at international conferences and schools throughout the year, with various invited contributions.

 

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Figure (by Simo Huotari): A part of an interior of a prototype Li-ion battery, measured with three-dimensional x-ray-diffraction-contrast imaging, using an inelastic x-ray scattering spectrometer at beamline ID20 of the ESRF. Red layer is a cathode,  below which is located Li metal (mostly blue). Red regions within the Li metal are Li crystallites with an orientations that match diffraction conditions toward the spectrometer. From a study in collaboration with the Delft University of Technology (The Netherlands) and ESRF.

vial

Figure (by Simo Huotari): X-ray transmission image of a vial containing sorbitol, 17 days after initially preparing the sorbitol in the amorphous state. The overlay shows the mapping of x-ray diffraction intensity indicating the areas where the sorbitol has started to crystallize. From a study done in collaboration with the Faculty of Pharmacy.