Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 86: Electronic Structure of Surfaces: Spectroscopy, Surface States II

O 86.10: Talk

Thursday, March 20, 2025, 17:15–17:30, H2

Single Hemisphere & Time-of-Flight Hybrid Photoelectron Momentum Microscopy — •Olena Tkach¹, Matthias Schmitt^2,3, Deepnarayan Biswas², Olena Fedchenko¹, Jieyi Liu², Hans-Joachim Elmers¹, Michael Sing³, Ralph Claessen³, Tien-Lin Lee², and Gerd Schönhense¹ — ¹JGU Mainz, Germany — ²DIAMOND, Didcot, United Kingdom — ³Universität Würzburg and Würzburg-Dresden Cluster of Excellence ct.qmat, Germany

The 2ns pulse period of the photon beams from most synchrotrons is too short for pure time-of-flight (ToF) photoelectron spectroscopy. With the use of a hemispherical analyzer (HSA) as a pre-filter, ToF momentum microscopy becomes possible at such high pulse rates. The first hemisphere & ToF hybrid MM is operated at the soft X-ray branch (photon energies from 105 eV to 2 keV) of beamline I09 at DIAMOND. The HSA reduces the transmitted energy band to typically 0.5 eV, which is then dispersed by ToF recording. In the first experiments the total efficiency gain when switching from the standard 2D (k_x,k_y) to the 3D (k_x,k_y,E_kin) hybrid mode was about 25. It is determined by the number of resolved kinetic energies (here 12) and the transmission factor of the electron optics due to the higher pass energy (500 eV) of the HSA in hybrid mode. The α²- term and the transit time spread due to different path lengths in the HSA are numerically corrected. The performance was validated by studying the well-known electronic structure of Au(111) and Cu(111), including circular dichroism (CDAD) measurements. The high efficiency was exploited in a series of measurements on the Kagome metal CsV₃Sb₅.

Keywords: ToF Momentum Microscope; Hemisphere; Hybrid mode; Soft X-ray; CDAD