Mainz 2017 – scientific programme

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A: Fachverband Atomphysik

A 38: Atoms in Strong Fields II

A 38.8: Talk

Friday, March 10, 2017, 16:15–16:30, N 2

Electron vortices in femtosecond multi-photon ionization — •Dominik Pengel, Stefanie Kerbstadt, Daniela Johannmeyer, Lars Englert, Tim Bayer, and Matthias Wollenhaupt — Universität Oldenburg, Institut für Physik, Carl-von-Ossietzky-Straße 9-11, 26129 Oldenburg

We demonstrate the generation of vortex-shaped photoelectron wave packets from multi-photon ionization of potassium atoms with sequences of two time-delayed, counterrotating circularly polarized femtosecond laser pulses. The electron vortices are measured by velocity map imaging spectroscopy and reconstructed using tomographic techniques. Weak-field excitation produces 6-arm Archimedean spirals. A change from c6 to c4 rotational symmetry of the vortices is observed for non-perturbative laser atom interaction. In addition, the influence of the time-delay on the vortex shape is discussed and an outlook towards ultra-broadband excitation using few-cycle pulses is given.