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, covering ~300 nm bandwidth around 3.3 μm with 6 GHz spectral resolution and 20 μs 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.
Highlights
Dual-comb spectroscopy can provide broad spectral bandwidth and high spectral resolution in a short acquisition time, enabling time-resolved measurements
Various optical frequency comb spectroscopy (OFCS) techniques have been utilized in the mid-IR wavelength region; e.g. combining an optical frequency comb with a mechanical FTS12,13, dual-comb spectroscopy (DCS)[14,15,16,17,18] and dispersion-based methods[19,20,21,22]
In the visible range (~530 nm), cavity-enhanced transient absorption spectroscopy (CE-TAS) has been demonstrated for study of the ultrafast dynamics of I2 in a molecular beam[32], and more recently, time-resolved dual-comb spectroscopy (TRDCS) has been reported for measurement of number density and temperature in a laser-induced plasma by monitoring three excited-state transitions of Fe33
Summary
Dual-comb spectroscopy can provide broad spectral bandwidth and high spectral resolution in a short acquisition time, enabling time-resolved measurements. 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. The former exhibits very long measurement times due to the step-scanning, while the latter yields shorter measurement times, but usually has a coarse spectral resolution In contrast to these traditional broadband methods, optical frequency comb spectroscopy (OFCS) simultaneously provides a broad spectral coverage and a high spectral resolution. We report time-resolved dual-comb spectroscopy (TRDCS) in the mid-IR wavelength region by nonlinear conversion of near-IR combs emitted from mode-locked lasers, and demonstrate its application for monitoring fast chemical dynamics. We study the vibrational excitation/de-excitation of CH4 in an electrical discharge and the concentration of the reaction product C2H6, at millisecond and microsecond time scales, while the discharge is modulated between dark and glow regimes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
