Mainz 2026 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 11: Atomic Systems in External Fields I
A 11.2: Vortrag
Dienstag, 3. März 2026, 11:30–11:45, N 2
Coherent control of helium photoelectron emission using ω–2ω SASE FEL pulses — •Harijyoti Mandal1, Muwaffaq Ali Mourtada1, Alexander Magunia1, Weiyu Zhang1, Yu He1, Hannes Lindenblatt1, Florian Trost1, Lina Hedewig1, Cristian Medina1, Arikta Saha1, Gergana D. Borisova1, Steffen Palutke2, Evgeny Schneidmiller2, Mikhail Yurkov2, Stefan Düsterer2, Rolf Treusch2, Chris H. Greene3, Yimeng Wang3, Robert Moshammer1, Ulrike Frühling2, Christian Ott1, and Thomas Pfeifer1 — 1Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany — 2Deutsches Elektronen Synchrotron DESY, 22607 Hamburg, Germany — 3Purdue University, West Lafayette, IN 47907, USA
Extreme-ultraviolet (XUV) free-electron lasers enable nonlinear ionization and interference between multiple excitation pathways, providing a platform for coherent control in the few-photon regime. We demonstrate phase-controlled ω-2ω photoionization of helium using stochastic SASE pulses at FLASH2, DESY Hamburg. Interference between one-photon (2ω) and two-photon (ω+ω) channels produces a tunable left-right asymmetry in the photoelectron angular distribution. Thin aluminium foils (100-300nm) imprint a calibrated dispersive phase shift between the fundamental (ω = 21.2eV) and second harmonic (2ω = 42.4eV). Fully differential momentum distributions were recorded with a reaction microscope and correlated shot-by-shot with spectral diagnostics, revealing asymmetry dependence on instantaneous photon energy, pulse intensity, and relative ω/2ω content.
Keywords: Coherent control; Photoelectron angular distributions (PADs); XUV nonlinear optics