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A: Fachverband Atomphysik
A 40: Strong laser fields - III
A 40.1: Invited Talk
Thursday, March 8, 2018, 14:00–14:30, K 2.019
Electron vortices — Dominik Pengel, Stefanie Kerbstadt, Lars Englert, Tim Bayer, and •Matthias Wollenhaupt — Carl von Ossietzky Universität, Oldenburg, Germany
Recently, the emergence of vortex structures in the momentum distribution of free electron wave packets from photoionization of atoms with sequences of two time-delayed counterrotating circularly polarized (CRCP) ultrashort laser pulses was predicted [1] and demonstrated experimentally [2]. Electron vortices arise from the superposition of two time-delayed free electron wave packets with different magnetic quantum numbers. In our experiment three-dimensional electron vortices are generated by multiphoton ionization of potassium atoms using CRCP femtosecond laser pulses from a polarization-shaped supercontinuum source [3] and reconstructed tomographically from velocity map imaging (VMI) measurements [4]. Absorption of another photon in the continuum changes the c6 azimuthal symmetry of the threshold vortex into c8 for above threshold ionization (ATI) [5]. Electron vortices from non-perturbative excitation show c4 azimuthal symmetry and a π-phase jump in the polar direction. Currently, we study electron vortices generated by bichromatic polarization-shaped CEP-stable supercontinua [3].
[1]J. M. Ngoko Djiokap et al., Phys. Rev. Lett. 115, 113004 (2015).
[2]D. Pengel et al., Phys. Rev. Lett. 118, 053003 (2017).
[3]S. Kerbstadt et al., Opt. Express 25, 12518 (2017).
[4]S. Kerbstadt et al., New J. Phys. 19, 103017 (2017).
[5]D. Pengel et al., Phys. Rev. A 96, 043426 (2017).