Benchmark measurements of absolute frequencies and collisional line-shape parameters in the CO-Ar system using comb-based FTS

Abstract

We report absolute frequency measurements of the CO fundamental band, together with high-precision Ar-induced collisional line-shape parameters using comb-based Fourier-transform spectroscopy. High-quality spectra were obtained with a stable mid-IR optical frequency comb source and careful suppression of technical noise. By applying analysis methods that fully exploit the advantages of optical frequency comb spectroscopy, precise frequency calibration and robust multi-line fitting were achieved, resulting line-center fitting errors below 0.00001 cm$^{-1}$ for most transitions. The measured transition frequencies agree with HITRAN within 0.0001 cm$^{-1}$, supporting the reliability of the semi-empirical database. Multi-line fits using a speed-dependent Voigt profile yield collisional parameters for approximately 40 P- and R-branch lines, providing a reliable experimental benchmark for CO-Ar line-shape modeling.