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Research - introduction

X-radiation is the light for going into the depth. It has the appropriate energy to penetrate and explore matter on a macroscopic as well as on an atomic scale. In atoms deep core holes can be created in order to investigate the fundamental reactions of the many electron system to this “deep” perturbation. X-ray absorption and emission/fluorescence can be utilized as highly sensitive “fingerprints” of the acting atom and its chemical environment. On the macroscopic scale matter can be illuminated and investigated within depths ranging up to the cm regime.

On the other hand, X-radiation is also the light for the micro- and nanotechnologies. It has the appropriate wavelength for structural investigation and manipulation of matter on the micro- and nanometer scale. The latter is only possible since the advent of efficient X-ray optics and the use of synchrotron radiation. Since the installation of dedicated synchrotron sources in the 1970`s and more recently the advent of coherent sources such as free electron lasers, X-ray science and technology see an enormous revival and development.

The research group Analytical X-ray Physics aims at the development of novel instrumentation as well as analytical methodology in the large field of X-ray science. The projects range from fundamental research concerning e.g. the investigation of dynamic processes in biomolecules to the adaptation of methodology to optimally analyze samples from biomedicine, catalysis or cultural heritage to the very practical designing and construction of novel laboratory instrumentation.

Subdivisions

XRF for the investigation of wall paintings in Petra
Lupe
Angle-resolved XRF
Lupe
(Confocal) micro-XRF
Lupe
NEXAFS spectroscopy
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X-ray microscopy
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Chemical speciation with hard X-rays
Lupe

Current projects

The main thrust of our research activities during recent years has focused on X-ray fluorescence spectroscopy (XRF) in terms of experimental innovations, in terms of quantification models, and in terms of new fields of application.

The inherent capability of X-rays to probe the inside of matter has triggered the advent of different depth resolved techniques. In our group 3D micro X-ray fluorescence spectroscopy (3D micro-XRF) and 3D micro X-ray absorption spectroscopy (3D micro-XAFS) have been developed and enable the three-dimensionally resolved reconstruction of elemental composition (3D micro-XRF) and chemical speciation, respectively. The depth resolution here lies in the order of a few tens of micrometers.

For the investigation of nano-structured material, such as solar cells, depth resolution in the nm-regime is necessary. For this purpose new synchrotron based techniques such as reference-free grazing incidence XRF (GIXRF) and GIXRF near edge X-ray absorption spectroscopy (NEXAFS) are currently employed in close cooperation with the Physikalisch-Technische Bundesanstalt (PTB) at the electron storage facility BESSY II in order to find optimal analytical strategies.

Additionally we are working on new X-ray sources, optics and detectors which facilitate such investigations in the laboratory. A flexible high vacuum spectroscopy chamber is available which allows the use of different sources, optics and detectors with the aim to perform nm-depth resolved investigations in the laboratory. Another project is the design and realization of novel von-Hamos-spectrometers based on HAPG crystals. These spectrometers render chemical speciation with an X-ray tube in the laboratory feasible. In a different project an innovative laser-produced plasma source  for the soft X-ray region was build up in cooperation with the Max-Born-Institute (MBI) in Berlin. This new X-ray source is optimized for the excitation of L-shells of transition metals for nm-resolved X-ray emission measurements as well as for X-ray absorption spectroscopy in the range between 100 and 1300 eV.

The inherent non-destructiveness of X-ray techniques renders the study of valuable cultural heritage objects feasible. In a joint project with the Department of Archaeology at Humboldt University we are developing characterisation, conservation and preservation procedures of specific remains of ancient Nabataean paintings on wall plaster and on sculpture.

The short wavelength and the high penetration depth of X-rays enable X-ray microscopy of µm sized objects with lateral resolutions down to 30 nm. We operate a laboratory soft X-ray microscope based on a laser-produced plasma source and are currently developing a scanning soft X-ray fluorescence microscopy end station for the use at PETRAII and Flash in Hamburg.

Zusatzinformationen / Extras

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Prof. Dr. Birgit Kanngießer
+49 (0)30-314 21428
Eugene-Paul-Wigner
Raum EW 346

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Sabine Remus
+49-(0)30-314-24887
Eugene-Paul-Wigner
Raum EW 343

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