The spectral transmission of carbon monoxide, nitrous oxide, and mixtures of the two has been studied in the 2200-cm-1 region, where overlapping absorption bands occur. With spectral slit widths sufficiently large to include several absorption lines, it was found that the observed spectral transmittance of a mixture is equal to the product of the transmittances of the components measured separately, provided that sufficient nitrogen is added to give the same total pressure for all samples. This result was also obtained for overlapping bands of nitrous oxide and methane in the 1300-cm-1 region. The present work confirms Burch’s earlier studies of overlapping bands of CO2 and water vapor. An investigation of the possible breakdown of the multiplicative property of transmission for narrow spectral slit widths was inconclusive.
Gary M. Hoover, Charles E. Hathaway, and Dudley Williams, "Infrared Absorption by Overlapping Bands of Atmospheric Gases," Appl. Opt. 6, 481-487 (1967)