Recollision scenario without tunneling: role of the ionic core potential

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Optics
• Strong Field Physics

Background:

• The standard three-step model for high harmonic generation (HHG) assumes electron tunneling and neglects the ionic core potential after ionization.
• Existing models often simplify the complex electron-ion dynamics during the recollision phase.

Purpose of the Study:

• To present a purely classical recollision scenario that fully accounts for the ionic core potential at all stages.
• To investigate the role of periodic orbits in driving electron recollisions.
• To connect the classical scenario to the standard three-step model and explain discrepancies.

Main Methods:

• Development of a classical recollision model incorporating the full ionic core potential.
• Analysis of electron trajectories and identification of key periodic orbits.
• Comparison of the classical model predictions with the established three-step model.

Main Results:

• A purely classical recollision scenario, valid at all intensities, is established without invoking quantum tunneling.
• A specific periodic orbit is identified as the primary driver of electron recollisions.
• The classical model successfully connects to the three-step model at high intensities, explaining its accuracy in predicting HHG cutoffs.

Conclusions:

• The ionic core potential plays a critical role throughout the recollision process, even at high intensities.
• Periodic orbits are fundamental to understanding electron recollision dynamics in strong fields.
• The classical model provides a more complete picture of HHG, offering insights into the limitations of simplified models.