High-order Harmonic Generation in a Time-integrated Quantum Transition Picture

TL;DR

This paper introduces a numerical approach to study high-order harmonic generation in laser-matter interactions, revealing the roles of continuum electrons and excited states, and highlighting laser-intensity effects on molecular HHG.

Contribution

A novel quantum simulation method that traces electronic states to analyze the mechanisms of high-order harmonic generation in molecules.

Findings

Continuum electrons with broad energy distributions contribute equally to harmonics.

Excited states significantly influence molecular HHG.

Laser intensity affects intramolecular interference patterns.

Abstract

We develop a numerical scheme to investigate the high-order harmonic generation (HHG) in intense laser-matter interactions. Tracing the time evolution of every electronic laser-field-free state, we "observe" the HHG in a time-integrated quantum transition picture. Our full-quantum simulations reveal that continuum electrons with a broad energy distribution contribute equally to one harmonic and the excited state also plays an important role in the molecular HHG. These results imply a laser-intensity-dependent picture of intramolecular interference in the HHG.