Darmstadt 2008 – scientific programme

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A: Fachverband Atomphysik

A 31: Interaction with intense laser pulses III: VUV and X-ray light

A 31.6: Talk

Friday, March 14, 2008, 15:15–15:30, 3D

Nonresonant inelastic x-ray scattering as a tool to study soft x-ray absorption edges using hard x rays: giant dipole resonances in barium and iodine compounds — •Christian Sternemann¹, Henning Sternemann¹, John S. Tse², and Metin Tolan¹ — ¹Fakultät Physik / DELTA, Technische Universität Dortmund, Dortmund, Germany — ²Department of Physics & Engeneering Physics, University of Saskatchewan, Saskatoon, Canada

Giant dipole resonances are collective excitations which can be found in systems ranging from atoms, clusters to solids. These phenomena are usually studied by soft x-ray absorption, photoelectron and electron energy loss spectroscopy. With the advent of third generation synchrotron radiation sources, nonresonant inelastic x-ray scattering of core shell excitations became a prominent tool to study truly bulk sensitive shallow absorption edges with high energy photons. This technique is not only restricted to dipole transitions but can access final states of different symmetry employing its momentum transfer dependence. Especially, low energy excitations can be studied under high pressure. Giant resonances were measured in barite, several complex barium-silicon compounds and iodine-silicon clathrate. For the barium compounds the shape of the giant resonance is modulated depending on the environment the resonating barium atoms are embedded in. The onset of the resonance could be measured within a high pressure environment for the structure I barium intercalated silicon clathrate. Moreover, for iodine-silicon clathrate it was observed that the resonance is strongly suppressed for high momentum transfers.