A uniform flow-cavity ring-down spectrometer (UF-CRDS): A new setup for spectroscopy and kinetics at low temperature

Area of Science:

• Physical Chemistry
• Astrophysical Chemistry
• Spectroscopy

Background:

• Low-temperature reaction kinetics and spectroscopy are crucial for understanding astrophysical environments.
• Previous methods limited the study of species and phenomena within uniform flows.

Purpose of the Study:

• To introduce and validate a novel Uniform Flow-Cavity Ring Down Spectrometer (UF-CRDS) setup.
• To enable high-resolution spectroscopy and kinetics studies of various species at low temperatures within uniform flows.
• To expand the investigation of hydrocarbon chain and polycyclic aromatic hydrocarbon (PAH) chemistry relevant to astrophysics.

Main Methods:

• Coupling a pulsed uniform (Laval) flow with continuous wave cavity ring-down spectroscopy (CRDS) in the near-infrared.
• Utilizing the CRESU (reaction kinetics in uniform supersonic flows) technique combined with the SKaR (Simultaneous Kinetics and Ring-Down) approach.
• Monitoring entire reactions during intensity decay within a high-finesse cavity for kinetic measurements.

Main Results:

• The UF-CRDS system provides high resolution and sensitivity for absorption spectroscopy in uniform flows.
• The setup successfully probed electronic and rovibrational transitions, extending detection capabilities.
• Demonstrated the technique's efficacy by studying the reaction between CN (v = 1) and propene at low temperatures.

Conclusions:

• The UF-CRDS is a powerful new tool for investigating low-temperature chemical phenomena and kinetics.
• This approach opens new avenues for studying reactive species, intermediates, and astrochemically relevant molecules.
• The results are consistent with previous studies, validating the UF-CRDS technique.