Preliminary interpretation of the infrared intensities of combination and difference bands of N2O and CO2.

Expressions derived by Overend for the infrared absorption of combination and difference bands are tested against experimental data for N2O and CO2(ν3±ν1, ν3±ν2, and ν1±ν2, where data are available). From these comparisons, values of the electrical anharmonicities Pαss′(=∂2pα /∂qs∂qs′) are obtained. Overend’s prediction of an anomalously higher value for the transition moment of certain difference bands than for the corresponding combination bands is verified. For CO2, mechanical anharmonicity dominates the intensities perdicted for combination and difference bands; for N2O, electrical anharmonicity is comparable in its contribution to the intensities of combination and difference bands.