Retrieval of Gas Temperature and Pressure Based on Rayleigh–Brillouin Spectrum

Abstract

Optical detection methods such as Rayleigh-Brillouin scattering spectrum can be used for physical parameter measurement in solids, liquids, and gas. In this paper, a new method based on spectral characteristics is proposed to realize temperature and pressure retrieval simultaneously in gas. The characteristics of Rayleigh-Brillouin spectrum are firstly utilized to establish the retrieval model by fitting Tenti-S6 line shape with 3Voigt model at different temperatures and pressures, and then deriving the retrieval equations via regression fitting procedure. Through theoretical and measured error analyses, the characteristic retrieval model based on Rayleigh linewidth and the whole linewidth of Rayleigh-Brillouin scattering spectrum is shown to be optimal. Afterward, the retrieval model is verified using the experimental Rayleigh-Brillouin scattering spectra of N 2 and air. The results indicate that, compared with the current method based on the whole linewidth or line shape of spectrum, the proposed method not only produces lower theoretical and retrieval errors but also can simultaneously retrieve the temperature and pressure of gases. The novel retrieval method provides a new idea for obtaining valuable information on gas parameters and promotes the application of Brillouin lidar remote sensing in meteorology and space science.