Integration log rotational-state distribution thermometry for multi-component gas temperature measurement using dual-comb spectroscopy

In this study, we propose a novel, to our knowledge, technique called integration log rotational-state distribution thermometry (ILRDT) for accurately estimating the temperatures of multiple gas species based on the integrated absorbance extracted from absorbance spectra using dual-comb spectroscopy. Although the integrated absorbance depends on temperature and is affected by pressure and concentration, the proposed ILRDT technique allows temperature estimation with low sensitivity to these parameters. To validate the effectiveness of this method, numerical simulations and experiments were conducted for 12 C 2 H 2 and H 13 CN at room temperature. Consequently, the gas temperatures were independently estimated with a relative error of less than 0.6% for both species. The ILRDT technique relaxes the strong molecule-specific constraints inherent to conventional RDT, thereby extending its applicability beyond acetylene to chemically distinct molecules such as H 13 CN, while retaining its calibration-free nature. This enables reliable temperature estimation using only a small number of absorption lines. These features make it a promising technique for rapid and high-precision gas thermometry applicable to a wide range of practical scenarios.