SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 22: Poster Session II: New methods II
O 22.6: Poster
Montag, 1. März 2021, 13:30–15:30, P
Single-Hemisphere Photoelectron Momentum Microscope with Time-of-Flight Recording — •Gerd Schönhense, Sergey Babenkov, Dmitry Vasilyev, Hans-Joachim Elmers, and Katerina Medjanik — Johannes Gutenberg-Universität, Institut für Physik, 55128 Mainz, Germany
Photoelectron momentum microscopy is an emerging powerful method for angle-resolved photoelectron spectroscopy (ARPES). These instruments record kx - ky images, typically exceeding a full Brillouin zone. As energy filters double-hemispherical [1] or time-of-flight (ToF) [2] devices are in use. Here we present a new approach for momentum mapping of the full half-space, based on a large single hemispherical analyzer [3]. Excitation by an unfocused He lamp yielded an energy resolution of 7.7 meV. The method circumvents the preconditions of previous theoretical work on the resolution limitation due to the alpha-square term and the transit-time spread (detrimental for time-resolved experiments). Data recording in the Fourier plane allows for large range of entrance angles in the analyzer (up to ± 7∘, opposed to typically ± 2∘ in conventional analyzers). A dispersive-plus-ToF hybrid mode with ToF analyzer behind the exit slit yields a gain up to N2 in recording efficiency (N number of resolved time slices). A key application will be ARPES at sources with high pulse rates like synchrotrons with 500 MHz time structure; the prototype will be installed at Diamond, UK. [1] C. Tusche et al., Ultramicrosc. 159, 520 (2015); [2] K. Medjanik et al., Nature Mat. 16, 615 (2017); [3] G. Schönhense et al., Rev. Sci. Instrum. 91, 123110 (2020).