SAMOP 2023 – scientific programme

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MO: Fachverband Molekülphysik

MO 3: Interaction with Strong or Short Laser Pulses I (joint session A/MO)

MO 3.1: Invited Talk

Monday, March 6, 2023, 11:00–11:30, F303

Time-resolved Kapitza-Dirac effect — •Kang Lin, Maksim Kunitski, Sebastian Eckart, Alexander Hartung, Qinying Ji, Lothar Schmidt, Markus Schöffler, Till Jahnke, and Reinhard Dörner — Goethe University

The Kapitza-Dirac effect describes that that an electron beam can be diffracted when passing through a light standing wave. In analogy to optical diffraction, the incident electron beam behaves like a wave, while the light standing wave plays the role of the grating. The Kapitza-Dirac effect serves as an optical diagnosis of the electron property in frequency domain. However, with the advent of pulsed laser technique, the ultrafast time information is imprinted in both the electron wavepacket and the light standing wave. It is totally unclear how an electron wavepacket will be diffracted by an ultrafast light standing wave. Here, a principle new phenomenon, termed as time-resolved Kapitza-Dirac effect, is discovered. We track the spatiotemporal evolution of an electron wavepacket diffracted by an ultrafast femtosecond (10-15 seconds) light standing wave. By scanning the time delay between the electron wavepacket and the standing wave, we observe so far unseen quantum interference effects. We show that the momentum spacing between diffraction peaks decreases continuously with the time delay increasing, which can be fractions instead of multiply integers of 2-photon momenta. The time-resolved Kapitza-Dirac effect can directly measure the chirp of the electron wavepacket optically.