Mainz 2026 – scientific programme
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A: Fachverband Atomphysik
A 41: Interaction with Strong or Short Laser Pulses II
A 41.4: Talk
Friday, March 6, 2026, 12:00–12:15, N 2
Strong-field ionization and electron diffraction in standing waves — •Tobias Heldt, Jan-Hendrik Oelmann, Lennart Guth, Lukas Matt, Anant Agarwal, Thomas Pfeifer, and José R. Crespo López-Urrutia — Max-Planck-Institut für Kernphysik, Heidelberg, Germany
Achieving the intensities required for strong-field effects, such as multiphoton ionization (MPI), usually relies on kilohertz-rate amplified laser systems. We employ a femtosecond enhancement cavity seeded by a near-infrared frequency comb to reach intensities exceeding 1013 W cm−2 at a repetition rate of 100 MHz. The bow-tie cavity supports counter-propagating pulses that form a transient standing wave at the focus. Combined with a gas jet and velocity-map imaging (VMI) [1], this setup allows angle-resolved photoelectron spectroscopy to compare traveling- and standing-wave ionization.
The standing wave doubles the peak intensity and compresses the interaction volume from the Rayleigh length to the < 200 fs pulse-overlap region, enabling momentum imaging without electrostatic refocusing [2]. Furthermore, the spatially periodic ponderomotive potential of a standing wave diffracts electrons (Kapitza-Dirac effect), reshaping the momentum distribution. We aim to time-resolve the diffraction dynamics using an additional interferometer that generates two successive standing waves.
[1] J.-H. Oelmann et al., Rev. Sci. Instrum., 93(12), 123303 (2022).
[2] T. Heldt et al., Opt. Lett. 49, 6825-6828 (2024).
Keywords: Multiphoton Ionization; Velocity-Map Imaging; Standing Wave; Kapitza-Dirac; Enhancement Cavities