High-harmonic probing of electronic coherence in dynamically aligned molecules

Area of Science:

• Quantum dynamics
• Molecular spectroscopy
• Attosecond science

Background:

• Coherent electron wave packets are fundamental to understanding molecular dynamics.
• High-harmonic spectroscopy (HHS) is a powerful tool for probing electronic structure.
• Measuring and controlling electronic coherence remains a significant challenge.

Purpose of the Study:

• To introduce and demonstrate a novel approach for measuring coherent electron wave packets.
• To investigate the role of electronic coherence in high-harmonic generation.
• To achieve unprecedented sensitivity in detecting weak electronic coherences.

Main Methods:

• Utilizing high-harmonic spectroscopy (HHS) with dynamically aligned nitric oxide molecules.
• Preparing molecules in a coherent superposition of electronic states.
• Exploiting optical interference between coherent and incoherent pathways.

Main Results:

• Observed previously unobserved high-harmonic generation channels linked to electronic coherence.
• Tracked the temporal evolution of electronic coherence coupled to nuclear motion.
• Demonstrated a conversion of 0.1% excitation fraction into a ~20% signal modulation due to interference.

Conclusions:

• Electronic coherence opens new pathways in high-harmonic generation.
• The developed HHS method provides highly sensitive detection of electronic coherence.
• This technique offers new insights into light-matter interactions and molecular dynamics.