RADIATION FEATURES OF MOLECULAR GAS MIXTURES

The nature of thermal radiation from a layer of dense gas in local thermodynamic equilibrium with radiation is considered. The radiation spectrum of a gas layer containing a mixture of molecular gases and microparticles consists of a large number (hundreds and thousands) of peaks that rise above the pedestal corresponding to microparticle radiation. Changes in partial radiation fluxes with varying concentration of one of the active components are investigated. Information on molecular radiation parameters contained in the HITRAN database is of great importance for the analysis and calculations. It is shown that the model of a homogeneous atmosphere with spectrum averaging for one or all components is unreliable when analyzing radiation flux changes resulting from concentration changes of one of the radiating components. This model is only convenient for estimating integral parameters of gas radiation. The dense cloud model assumes that radiation in different directions of the layer is determined by different spatial regions that do not affect each other, and also assumes a sharp boundary for dispersed phase radiation. This model works better with increasing optical thickness of the layer relative to molecular components. The accuracy and capabilities of the dense cloud model are demonstrated by calculations of radiation fluxes generated by the standard atmosphere in the absorption bands of carbon dioxide molecules. A fundamental difference is shown between radiation flux changes from an optically dense gas layer with varying temperature when changing the concentration of an active component for single-component and multi-component systems. In a single-component gas, the change in partial radiation flux due to concentration changes of the radiating component is proportional to the temperature gradient, while in a multi-component gas, the change in partial radiation flux of a given component is almost compensated by reverse changes due to absorption by other components. A five-fold error in climate models for global temperature change due to changes in atmospheric carbon dioxide concentration is shown, as these models neglect the absorption of additional carbon dioxide radiation by water molecules and clouds. Additionally, the presented algorithms can serve as a basis for creating radiation amplifiers in the laser transition region for carbon dioxide with wavelengths near 9.5 μm and 10.6 μm. These amplifiers are suitable for monitoring combustion sources on Earth’s surface from satellites, as well as engines and power plants using fuel combustion. The sensitivity of these laser amplifiers exceeds that of modern thermal imagers by orders of magnitude, and the specified spectral lines of laser transitions for amplification fall within the atmospheric transparency window.