On the significant enhancement of the continuum-collision induced absorption in H2O+CO2 mixtures

•Infrared spectra of H2O+CO2 mixtures were recorded and processed.•The binary absorption coefficients for mixed gases were obtained.•The results show significantly enhanced absorptions in the regions around 9 and 4 μm.•The data are discussed in regard a molecular band shape formation.

The IR spectra of water vapor–carbon dioxide mixtures as well as the spectra of pure gas samples have been recorded using a Fourier-transform infrared spectrometer at a resolution of 0.1 cm−1 in order to explore the effect of colliding CO2 and H2O molecules on their continuum absorptions. The sample temperatures were 294, 311, 325 and 339 K. Measurements have been conducted at several different water vapor partial pressures depending on the cell temperature. Carbon dioxide pressures were kept close to the three values of 103, 207 and 311 kPa (1.02, 2.04 and 3.07 atm). The path length used in the study was 100 m. It was established that, in the region around 1100 cm−1, the continuum absorption coefficient CH2O+CO2CH2O+CO2 is about 20 times stronger than the water–nitrogen continuum absorption coefficient CH2O+N2CH2O+N2. On the other hand, in the far wing region (2500 cm−1) of the ν3 CO2 fundamental band, the binary absorption coefficient CCO2+H2OCCO2+H2O appears to be about one order of magnitude stronger than the absorption coefficient CCO2+CO2CCO2+CO2 in pure carbon dioxide. The continuum interpretation and the main problem of molecular band shape formation are discussed in light of these experimental facts.