Pressure and temperature retrieval of nitrogen respectively by analysis of spontaneous Rayleigh–Brillouin scattering profiles

Abstract In this paper, a gas–aerosol mixture is investigated and both Mie and Rayleigh–Brillouin features in the resulting spectrum are observed. The theoretical spontaneous Rayleigh–Brillouin scattering (SRBS) spectra of nitrogen with different intensity of Mie scattering under the pressure of 1atm, 3atm, 5atm and 7atm at 298K are first simulated to study the effect of Mie scattering on pressure and temperature retrieval. It is found that the relative pressure retrieval error and the absolute temperature retrieval error are below 3.0% and 1.0K respectively with strong Mie scattering. The SRBS spectra of nitrogen gas mixed with aerosols are then experimentally measured for a wavelength of 532 nm over the pressure range from 1atm to 8atm and at the temperature of 288.2K, 292.5K, 294.9K and 298.0K. Measured spectra are compared with the modeled spectra and the pressure and temperature parameters are separately retrieved where χ 2 (normalized chi-squared error) is at its minimum. The comparison results show that the pressure and temperature can be respectively and precisely retrieved based on the Tenti S6 model according to SRBS spectrum when Mie scattering exists. Meanwhile, the retrieval results agree with the theoretical simulation results well. The relative error between the retrieved and the reference pressure is less than 2.1% and the absolute error between the retrieved and the reference temperature is below 3.0K. It is demonstrated that the scattering angle uncertainty and signal-to-noise ratio (SNR) of the measured SRBS spectra are the main factors affecting the accuracy of parameter retrieving.