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O: Fachverband Oberflächenphysik

O 106: Electronic Structure of Surfaces: Spectroscopy, Surface States III

O 106.2: Vortrag

Freitag, 24. März 2017, 10:45–11:00, WIL C107

Circular Dichroism in Soft X-ray Photoelectron Diffraction — •Katerina Medjanik^1,2, Gunnar Öhrwall², Olena Fedchenko¹, Sergey Chernov¹, Anna Zaporozhchenko-Zymaková¹, Andreas Oelsner³, Benedikt Schönhense⁴, Hans- Joachim Elmers¹, and Gerd Schönhense¹ — ¹Univ. Mainz — ²MAX IV Lund — ³Surface Concept GmbH Mainz — ⁴Imperial College London

The interference patterns in the angular distribution of electrons from core levels due to photoelectron diffraction (PED) give valuable information on the short-range order around the emitter atom. For circularly polarized excitation, the PED patterns contain sizeable circular dichroism in the angular distribution (CDAD), originating from the interference of final-state partial waves with different quantum numbers m_l [1]. Since a large region in k-space is observed simultaneously, momentum microscopy is ideal for the study of CDAD in PED. ToF (time-of-flight) energy discrimination [2] provides simple means for the selection of the desired core level even at very high photon pulse rates (here 100 MHz). We report first results for W(110) and Ir(111) taken at beamline I1011 at MAX II, Lund, Sweden. The diffraction patterns reveal pronounced dichroism in 4f core-level emission. The asymmetry maps A_CDAD (k_x,k_y,hv) vary strongly with photon energy between hv=300 and 1000 eV. Funded by BMBF (05K13UM2). [1] Fecher et al., JESRP 122, 157 (2002); [2] Schönhense et al., JESRP 200, 94 (2015).