Author

Shota Sasaki, Tohoku University, Graduate School of Engineering, and Eleforming Technology, Inc.
Keisuke Takashima, Eleforming Technology, Inc.

Keywords

FT-IR absorption spectroscopy, Gas Analysis, HITRAN

Abstract

This report presents a database-assisted Fourier Transform Infrared (FT-IR) gas analysis method that enables calibration-free, simultaneous quantification of complex gas mixtures, with a demonstration of its effectiveness through applications using atmospheric-pressure plasmas. Gas analysis is essential in modern industrial and environmental systems. Particularly for new applications such as plasma-based gas conversion where numerous reactive species are generated from abundant resources such as air and water, however, conventional calibration-based techniques are impractical due to the large number of species, the presence of unknown components, and the difficulty of preparing standard gases.

To overcome these limitations, we developed an FT-IR analysis algorithm based on the HITRAN molecular absorption database. The method synthesizes theoretical absorption spectra by incorporating temperature, pressure, and instrumental functions, and determines gas compositions by least-squares fitting to measured spectra. This approach eliminates the need for calibration gases while maintaining high accuracy and enabling rapid, in-flow analysis.

The method is validated through the analysis of plasma-generated gas mixtures, showing excellent agreement between measured and simulated spectra over a wide spectral range, even under strong interference from species such as H₂O and CO₂. Furthermore, the technique enables detailed investigation of reaction pathways, leading to the selective synthesis of dinitrogen pentoxide (N₂O₅) from air.

The proposed method significantly enhances experimental throughput and provides a powerful tool for studying complex reaction systems, with broad applicability to sustainable nitrogen fixation, plasma chemistry, and industrial gas analysis.