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 γCO−He(T0) and γCO−O2(T0), respectively, while values of 0.53 ± 0.06 and 0.62 ± 0.04 were obtained for nCO − He and nCO−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 γCO−He(T0) and γCO−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.