Plasma perspective on strong field multiphoton ionization

TLDR

Strong‑field multiphoton ionization generates a wave packet at each laser peak, and within the first period the returning electron can acquire high kinetic energy, driving high‑harmonic generation, multiphoton two‑electron ejection, and above‑threshold ionization, with the effect strength governed by transverse wave‑packet spreading and laser polarization. Experimentalists should account for transverse wave‑packet spreading and laser polarization when planning future strong‑field multiphoton ionization experiments.

Abstract

During strong-field multiphoton ionization, a wave packet is formed each time the laser field passes its maximum value. Within the first laser period after ionization there is a significant probability that the electron will return to the vicinity of the ion with very high kinetic energy. High-harmonic generation, multiphoton two-electron ejection, and very high energy above-threshold-ionization electrons are all conssequences of this electron-ion interaction. One important parameter which determines the strength of these effects is the rate at which the wave packet spreads in the direction perpendicular to the laser electric field; another is the polarization of the laser. It will be essential for experimentalists to be aware of these crucial parameters in future experiments.