Accurate simulation of spontaneous Raman scattering of CO2 for high-temperature diagnostics

This paper presents a comprehensive simulation approach for the temperature-dependent Raman spectra of CO2, a common product in combustion and reactive environments. Previous studies have typically been limited to isotropic scattering or a restricted number of energy levels. In contrast, our simulation incorporates both isotropic and anisotropic scattering, including all ro-vibrational O, P, Q, R, and S transitions, and extends to all energy levels contained in and up to polyad 30, which our results demonstrate is essential for accurate modeling at high temperatures. The four most prevalent isotopologues 12 C 16 O 2 , 13 C 16 O 2 , 16O12C17O, and 16O12C18O are included, collectively accounting for over 99.99 % of naturally occurring CO2. Polarizability ratios between the v1 and 2 v 2 modes and the isotropic/anisotropic contributions were determined by fitting them to experimental spectra at 296 K. The simulated CO2 spectra demonstrate excellent agreement with experimental data across temperatures up to 2355 K, thereby enhancing the reliability of Raman spectroscopy in various applications involving CO2.