Inhalt des Dokuments
Chemical speciation with soft X-rays: ns-NEXAFS
- Ti L and O K absorption edges of a 150 nm thick TiO2 sample using 1500 and 300 SSM images, respectively (top) Bottom: a spectrum containing both edges of a 100 nm TiO2 sample using 2000 SSM images.
- © AG Kanngießer
Near edge X-ray absorption fine structure (NEXAFS) spectroscopy in the soft X-ray range enables the elucidation of the electronic structure of matter, be it in solid, liquid or gaseous form. The highly resolved investigation of the absorption edges reveals a fine structure which gives insight about oxidation state, bond lengths and angles as well as type and number of nearest neighbors. While this techniques is routinely performed at large scale facilities, the adaptation to laboratory equipment is challenging, especially for energies above 500 eV.
We have developed a laboratory setup using a laser-produced plasma (lpp) source  and a twin-arm reflection zone plate spectrometer . The high brightness of the lpp source and the efficiency of the slit-less spectrometer enable single shot spectroscopy with an X-ray pulse length between 500 ps and 30 ns rendering direct monitoring of dynamic processes feasible. By utilizing a part of the laser light used for plasma formation, a pump beamline is additionally facilitated. Thus, optical pump - X-ray probe experiments with ns time resolution and an energetic resolving power of E/ΔE ~ 1000 in the range between 200 eV and 1300 eV can be performed. The stability of the setup and optimized measurement modes result in a Poisson noise limited instrument with the possibility to measure changes in absorption down to 10-4.
Contact: Ioanna Mantouvalou , Adrian Jonas 
I. Mantouvalou, K. Witte, D. Grötzsch, M. Neitzel, S. Günther, J. Baumann, R. Jung, H. Stiel, B. Kanngießer, and W. Sandner, Review of Scientific Instruments 86, 035116 (2015)
I. Mantouvalou, K. Witte, W. Martyanov, A. Jonas, D. Grötzsch, C. Streeck, H. Löchel, I. Rudolph, A. Erko, H. Stiel, and B. Kanngießer, Applied Physics Letters 108, 201106 (2016)
A. Jonas, H. Stiel, L. Glöggler, D. Dahm, K. Dammer, B. Kanngießer, and I. Mantouvalou, Towards Poisson noise limited optical pump soft X-ray probe NEXAFS spectroscopy using a laser-produced plasma source, Optics Express, Vol. 27 (Issue 25, pp. 36524-36537), 2019