Time-resolved mid-infrared dual-comb spectroscopy

TL;DR

This paper introduces the first time-resolved mid-infrared dual-comb spectroscopy technique, enabling high-resolution, broadband, and rapid monitoring of molecular dynamics in chemical reactions.

Contribution

It demonstrates a novel application of dual-comb spectroscopy in the mid-infrared range with temporal resolution of 20 microseconds, expanding capabilities for studying fast chemical processes.

Findings

Successfully monitored methane and ethane production in a plasma discharge.

Achieved 6 GHz spectral resolution over 300 nm bandwidth.

Observed vibrational and chemical dynamics in real-time.

Abstract

Dual-comb spectroscopy can provide broad spectral bandwidth and high spectral resolution in a short acquisition time, enabling time-resolved measurements. Specifically, spectroscopy in the mid-infrared wavelength range is of particular interest, since most of the molecules have their strongest rotational-vibrational transitions in this "fingerprint" region. Here we report time-resolved mid-infrared dual-comb spectroscopy for the first time, covering ~300 nm bandwidth around 3.3 {\mu}m with 6 GHz spectral resolution and 20 {\mu}s temporal resolution. As a demonstration, we study a CH4/He gas mixture in an electric discharge, while the discharge is modulated between dark and glow regimes. We simultaneously monitor the production of C2H6 and the vibrational excitation of CH4 molecules, observing the dynamics of both processes. This approach to broadband, high-resolution, and time-resolved mid-infrared spectroscopy provides a new tool for monitoring the kinetics of fast chemical reactions, with potential applications in various fields such as physical chemistry and plasma/combustion analysis.