Laser-induced distortion of structural interferences in high harmonic generation

TL;DR

This paper investigates how laser-driven electron dynamics affect two-center interferences in high harmonic generation from diatomic molecules, revealing spectral smoothing and phase-jumps that impact molecular spectroscopy.

Contribution

It provides a theoretical analysis showing the influence of laser field conditions on interference patterns and phase behavior in high harmonic generation.

Findings

Spectral smoothing of interferences depends on laser field at recombination.

Phase-jumps differ for short and long electron trajectories.

Harmonic emission is affected by electron dynamics beyond simple dipole proportionality.

Abstract

We study theoretically the two-center interferences occurring in high harmonic generation from diatomic molecules. By solving the time-dependent Schroedinger equation, either numerically or with the molecular strong-field approximation, we show that the electron dynamics results in a strong spectral smoothing of the interference, depending on the value and sign of the driving laser field at recombination. Strikingly, the associated phase-jumps are in opposite directions for the short and long trajectories. In these conditions, the harmonic emission is not simply proportional to the recombination dipole any more. This has important consequences in high harmonic spectroscopy, e.g., for accessing the molecular-frame recombination dipole in amplitude and phase.