Mainz 2026 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 22: Poster – Attosecond Physics (joint session A/MO)

A 22.6: Poster

Mittwoch, 4. März 2026, 17:00–19:00, Philo 1. OG

Phase control in XUV-assisted high-order harmonic generation — •Zeinab Hardani and Manfred Lein — Leibniz University Hannover, Institute of Theoretical Physics,30167 Hannover, Germany

We investigate high-order harmonic generation (HHG) driven by a combined extreme-ultraviolet (XUV) pulse combined with a strong infrared (IR) laser field. Single-photon absorption of the XUV pulse releases the electron with well-defined initial conditions, while the IR field governs its motion in the continuum and its recombination with the parent ion. We evaluate the harmonic phase in XUV-assisted HHG and identify four main contributions: the strong-field phase, the Coulomb phase from the long-range potential, the recombination phase from the transition dipole, and an additional ionization phase associated with XUV-assisted emission. To quantify these contributions, we solve the one-dimensional time-dependent Schrödinger equation (TDSE) for an atomic model driven by combined IR+XUV fields and compare the extracted phase with the theoretical methods: strong-field approximation, analytical R-matrix, and scattering-theory predictions. In addition, we employ a classical model including the Coulomb potential and the XUV-imposed initial velocity to obtain ionization and recollision times, these recollision times agree with those inferred from the TDSE. Overall, we show that the XUV field shifts ionization and recombination to later times, thereby delaying harmonic emission and reshaping the phase of attosecond electron trajectories in agreement with both quantum simulations and classical modeling, and offering a flexible route to control XUV-triggered HHG in time.

Keywords: high-order harmonic generation; electron trajectories; time-dependent Schrödinger equation; strong-field approximation; attosecond electron dynamics