Technological advances in recent decades have enabled the widespread use of terahertz (THz) instruments for a variety of applications including industrial inspection, security and defense, telecommunications, biomedical and gas sensing. In the gas phase, High-Resolution Frequency-Domain TeraHertz Spectroscopy (THz-FDS) offers a powerful tool for detecting a wide range of polar compounds at trace levels. For the first time, rotational spectroscopy has been applied within a simulation chamber for isotopic ratio determination and kinetic studies, opening up new perspectives for quantitative time-resolved spectroscopic analysis of greenhouse gas reactions relevant to high-altitude atmospheric chemistry. Despite its excellent selectivity and its ability to unambiguously identify between compounds in complex matrix, THz-FDS is mainly used for laboratory studies.
For this purpose, the potential of such spectroscopy as a tool for real-time diagnosis and monitoring of emissions regulated compounds at industrial sites has been the subject of intercomparison with certified instruments. Moreover, combined with a pre-concentration system to improve sensitivity, the spectrometer was able to detect VOCs at levels below ppm in atmospheric emissions, as well as in samples of exhaled air. These findings highlight the potential of THz spectroscopy not only for emission and process monitoring but also for broader air quality applications and medical issues.