High-temperature He- and O₂-broadening of the R(12) line in the 1←0 band of carbon monoxide

Line shapes of the R(12) line in the 1←0 band of CO were measured near 1 atm between 1100 and 2200 K in mixtures of helium and oxygen behind reflected shock waves. A quantum cascade laser was scanned over the R(12) line at 2190.0175 cm⁻¹ with a scan range of 0.4 cm⁻¹ and a scan rate of 2 kHz. Voigt profiles were fit to the measured line shapes. The temperature dependence of the broadening coefficient was assumed to take the form γ(T) = γ(T₀)(T₀/ T)ⁿ (T₀ = 296 K). By extrapolating from the high-temperature data, values of 0.048 ± 0.005 and 0.048 ± 0.004 cm⁻¹atm⁻¹ were obtained for γ_CO−He(T₀) and γ_CO−O2 (T₀), respectively, while values of 0.53 ± 0.06 and 0.62 ± 0.04 were obtained for n_{CO − He} and n_CO−O2 , respectively. For validation purposes, line shapes were also measured in argon mixtures; the resulting CO-Ar broadening parameters were in excellent agreement with recent literature values. Line shapes were also measured at room temperature in mixtures of CO/He and CO/O₂; excellent agreement was found between measured and historical values of γ_CO−He(T₀) and γ_CO−O2 (T₀). The general behavior of the broadening coefficient over a wide temperature range is discussed. The broadening parameters presented herein are useful for modeling CO-He and CO-O₂ broadening of the R(12), 1←0 transition between 1100 and 2200 K and are the first measurements of their kind.