Quantum path interferences in high-order harmonic generation from aligned diatomic molecules

TL;DR

This paper presents a novel method combining time-gated ion microscopy and pump-probe techniques to directly observe and measure electron quantum path interferences in high-order harmonic generation from aligned diatomic molecules, revealing their dependence on molecular orientation.

Contribution

It introduces a new experimental approach that allows direct in situ measurement of quantum interference phases in high-order harmonic generation from molecules, advancing understanding in strong-field molecular physics.

Findings

Successfully measured phase differences of quantum paths in harmonic emission

Demonstrated dependence of interference patterns on molecular alignment

Enabled in situ observation without auxiliary atomic references

Abstract

Electron quantum path interferences in strongly laser-driven aligned molecules and their dependence on the molecular alignment is an essential open problem in strong-field molecular physics. Here, we demonstrate an approach which provides direct access to the observation of these interference processes. The approach is based on the combination of the time-gated-ion-microscopy technique with a pump-probe arrangement used to align the molecules and generate high-order harmonics. By spatially resolving the interference pattern produced by the spatiotemporal overlap of the harmonics emitted by the short and long electron quantum paths, we have succeeded in measuring in situ their phase difference and disclose their dependence on molecular alignment. The findings constitute a vital step towards an understanding of strong-field molecular physics and the development of attosecond spectroscopy approaches without the use of auxiliary atomic references.