An apparatus for quantitative high-harmonic generation spectroscopy in molecular vapours

Area of Science:

• Physical Chemistry
• Spectroscopy
• Laser Physics

Background:

• High-harmonic generation (HHG) spectroscopy is a powerful tool for studying molecular electronic structure.
• Studying liquid-phase molecules using gas-phase spectroscopy presents significant challenges due to phase-matching and sample delivery.
• Existing methods often struggle to obtain clear spectra for complex molecules.

Purpose of the Study:

• To present a novel apparatus for performing gas phase high-harmonic generation spectroscopy on molecules typically found in the liquid phase.
• To overcome limitations in studying liquid-phase molecular dynamics using advanced spectroscopic techniques.
• To enable direct comparison of experimental data with theoretical models.

Main Methods:

• An apparatus was designed to heat liquid molecular samples, generating vapor for a continuous flow gas jet.
• Vapor pressures exceeding 1 bar were achieved, facilitating stable gas jet formation.
• High harmonic spectroscopy experiments were conducted using benzene as a sample with a 1.8 μm driving laser field.

Main Results:

• The developed system successfully generated gas-phase spectra for a liquid-phase molecule (benzene).
• The obtained spectra were nearly free from longitudinal phase-matching effects, a common artifact in HHG.
• The high quality of the spectra allows for direct comparison with advanced numerical simulations.

Conclusions:

• The novel apparatus provides a unique capability for gas phase spectroscopy of liquid-phase molecules.
• This technique significantly simplifies spectral analysis by minimizing phase-matching issues.
• The system opens new avenues for investigating molecular properties and dynamics with unprecedented accuracy.