Long-wave mid-infrared cavity-enhanced frequency comb spectroscopy of cold, complex molecules

TL;DR

This paper introduces a novel LWIR cavity-enhanced frequency comb spectroscopy instrument capable of high-resolution, broadband detection of cold, complex molecules, demonstrated through spectra of ethane and ethanol at different temperatures.

Contribution

The paper presents a new integrated setup combining a LWIR frequency comb, high-finesse cavity, cryogenic cooling, and Fourier transform interferometry for advanced molecular spectroscopy.

Findings

High-resolution spectra of ethane and ethanol in LWIR region

Effective cooling of molecules to cryogenic temperatures

Demonstration of broadband, sensitive detection capabilities

Abstract

We report the development of a new instrument for cavity-enhanced absorption spectroscopy of the fundamental rovibrational transitions of molecules in the long-wave mid-infrared (LWIR) region from 6500 to 10000 nm. Our setup combines a LWIR frequency comb, a high-finesse optical enhancement cavity, a cryogenic buffer gas cooling cell, and a Fourier transform interferometer to obtain broadband, high-resolution, and high-sensitivity molecular absorption spectra. Here, we showcase the capabilities of this setup by presenting the gas-phase LWIR spectra of the $\nu_6$ band of ethane and the $\nu_{10}$ band of the gauche conformer of ethanol near 7200 nm under both room temperature and cryogenic conditions.