Molecular internal dynamics studied by quantum path interferences in high order harmonic generation

TL;DR

This paper explores how quantum path interferences in high harmonic generation reveal intra-molecular electronic and nuclear dynamics, enabling attosecond spectroscopy of charge migration in molecules.

Contribution

It demonstrates the sensitivity of long electron trajectories to molecular nuclear dynamics and develops theoretical models linking quantum interferences to electronic motion.

Findings

Long trajectory signatures depend on molecular dynamics.

Quantum interferences encode electronic migration signatures.

Method enables self-referenced attosecond spectroscopy.

Abstract

We investigate how short and long electron trajectory contributions to high harmonic emission and their interferences give access to intra-molecular dynamics. In the case of unaligned molecules, we show experimental evidences that the long trajectory signature is more dependent upon the molecule than the short one, providing a high sensitivity to cation nuclear dynamics within 100's of as to few fs. Using theoretical approaches based on Strong Field Approximation and Time Dependent Schrodinger Equation, we examine how quantum path interferences encode electronic motion whilst molecules are aligned. We show that the interferences are dependent on channels superposition and upon which ionisation channel is involved. In particular, quantum path interferences encodes electronic migration signature while coupling between channels is allowed by the laser field. Hence, molecular quantum path interferences is a promising method for Attosecond Spectroscopy, allowing the resolution of ultra-fast charge migration in molecules after ionisation in a self-referenced manner.