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

,

,

, and

are included, collectively accounting for over 99.99 % of naturally occurring CO₂. Polarizability ratios between the $v_1$ and $2v_2$ 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.