Regensburg 2025 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 26: Focus Session Ultrafast Electron Microscopy at the Space-Time Limit III
O 26.4: Vortrag
Dienstag, 18. März 2025, 11:30–11:45, H2
Observation of Kapitza-Dirac effect with fast electrons — •Kamila Moriová1, Petr Koutenský1, Marius Constantin Chirita Mihaila1, Zbyněk Šobáň2, Andreas Schertel3, Jaromír Kopeček2, and Martin Kozák1 — 1Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic — 2Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic — 3Carl Zeiss AG, Oberkochen, Germany
Advancing ultrafast electron microscopy relies on coherent control of free electron wavefunctions. While most research focuses on electron interactions with optical near-fields, an all-optical approach using ponderomotive forces offers a promising alternative for manipulating pulsed electron beams. The Kapitza-Dirac effect [1], where free electrons diffract coherently from a standing light wave, enables momentum transfer via stimulated Compton scattering. However, its application has been limited to low-energy electrons due to challenges in resolving small deflection angles of electron beams caused by photon absorption and emission.
We report the observation of the Kapitza-Dirac effect in a scanning electron microscope using high-energy (20 keV) electrons. Photon sidebands in the electron transverse momentum spectrum are detected in a convergent beam diffraction geometry using spatial filtering. This effect can serve as a coherent electron beam splitter or phase plate in various types of electron microscopes and paves the way for exploring fundamental electron-light interactions.
[1] Freimund, D. L. et al. Nature 413, 142 (2001)
Keywords: ultrafast electron microscopy; free electron control; ponderomotive potential; Kapitza-Dirac effect