Mainz 2017 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 34: Atoms in Strong Fields I

A 34.1: Hauptvortrag

Freitag, 10. März 2017, 11:00–11:30, N 2

3d-Photoelectron Momentum Distributions from Multi-Photon Ionization with Ultra Short Polarization-Shaped Laser Pulses — •Matthias Wollenhaupt — Carl von Ossietzky Universität, 26129 Oldenburg, Germany

We present our experiments on multi-photon ionization of atoms with polarization-shaped femtosecond light pulses. In the first part, we demonstrate the generation of vortex-shaped photoelectron wave packets from resonance enhanced multi photon ionization (REMPI) of atoms with sequences of two time-delayed, counterrotating circularly polarized pulses from a supercontinuum femtosecond laser source. The electron vortices are measured by velocity map imaging (VMI) and reconstructed using tomographic techniques. In the second part, bichromatic polarization-shaped femtosecond laser pulses [1] are employed to manipulate photoelectron momentum distributions. We study REMPI by counterrotating circularly polarized and orthogonally linearly polarized bichromatic scenarios. The reconstructed 3d-photoelectron momentum distributions show different uncommon angular superposition states at different photoelectron energies. The analysis of the photoionization pathways reveals that REMPI by bichromatic polarization-shaped fields relies on the interplay of selection rules and intrapulse frequency mixing of spectral bands with different ellipticity. Finally, we use a bichromatic pump-probe scheme to follow the time evolution of an atomic spin-orbit wave packet observed in the 3d-photoelectron momentum distribution. [1] S. Kerbstadt, L. Englert, T. Bayer and M. Wollenhaupt, J. Mod. Opt., accepted (2016)