Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 8: Surface State Spectroscopy I

O 8.4: Talk

Monday, March 7, 2016, 11:30–11:45, H4

Fast Band-Mapping in the Soft X-Ray Range Using ToF Momentum Microscopy — •K. Medjanik^1,2, O. Fedchenko¹, S. Chernov¹, D. Kutnyakhov¹, B. Schönhense³, M. Ellguth¹, A. Oelsner⁴, S. Däster⁵, Y. Acremann⁵, T. Peixoto⁶, P. Lutz⁶, C.-H. Min⁶, F. Reinert⁶, J. Viefhaus⁷, W. Wurth^8,9, H.J. Elmers¹, and G. Schönhense¹ — ¹Institut für Physik, Uni-Mainz — ²MAX IV Lab., Lund, Sweden — ³Imperial College, London, UK — ⁴Surface Concept GmbH — ⁵ETH Zürich — ⁶EP 7, Uni-Wuerzburg — ⁷DESY, Hamburg — ⁸CFEL, Uni-Hamburg — ⁹Desy Photon Science

We present the first results of time-of-flight k-microscopy [1] using soft X-rays. The full 3D Brillouin zones of W and Ir were mapped at beamline P04 of PETRA III between hv=300 and 1300eV. Parallel acquisition of k-discs with 18,000 data points each and about 100 energies resulted in orders of magnitude higher speed and allowed us to operate the monochromator down to its resolution limit of 40,000 at 1000eV. The band features are sharp up to 1300eV at T=30K. Transfer of photon momentum manifests in the form of a rigid shift of the k_x,k_y-patterns and corresponding energy shift. The 40-bunch mode of PETRA provides an ideal pulse period of 192 ns. In order to adapt the ToF-microscope to multibunch conditions or to pump-probe conditions with low-repetitive lasers, a fast electrostatic chopper is developed [2].

Funded by BMBF (05K13UM2, 05K13GU3)

[1] G.Schönhense et al., JESRP 200 (2015) 94-118; [2] A. Zaporozhchenko et al., DPG 2016.