The effect of dressing on high-order harmonic generation in vibrating H$_2$ molecules

TL;DR

This paper develops a theoretical model for high-order harmonic generation in vibrating H₂ molecules, accounting for vibrational motion and laser-induced state coupling, revealing significant effects at long wavelengths.

Contribution

It introduces a strong-field approximation that includes vibrational dynamics and state coupling, advancing understanding of harmonic generation in molecules under intense laser fields.

Findings

Field dressing reduces harmonic yield at long wavelengths.

Vibrational motion influences harmonic signal ratios.

Isotope effects are modified by laser-induced state coupling.

Abstract

We develop the strong-field approximation for high-order harmonic generation in hydrogen molecules, including the vibrational motion and the laser-induced coupling of the lowest two Born-Oppenheimer states in the molecular ion that is created by the initial ionization of the molecule. We show that the field dressing becomes important at long laser wavelengths ($\approx 2 \mu$m), leading to an overall reduction of harmonic generation and modifying the ratio of harmonic signals from different isotopes.