Infrared Emissivity of Carbon Dioxide (27-µ Band)

Abstract

Simplified equations are developed for computing the spectral emissivity of the carbon dioxide 2 .7-µ band. The harmonic oscillator model is assumed in computing band intensities, but anharmonicity is considered in computing the spectral distribution of emitted radiation. Simplifying assumptions are made to account for the effects of Fermi resonance. Calculated values of S¯/d are presented for temperatures ranging from 300° to 3000°K, from which emissivities may be readily computed for a given optical path in the weak-line approximation. Calculated values of emissivity are also presented for temperatures ranging from 300° to 1500°K, for various optical depths, for the case of a pure Doppler line shape as well as for the weak-line approximation. Calculated values of 2α0½.S¯½./d are presented for temperatures ranging from 300° to 1200°K, from which emissivities may be computed in the strong-line approximation. The weak-line approximation is shown to be in reasonable agreement with published experimental data for 1200° to 1500°K. An explicit formula for the temperature variation of the integrated band intensity is shown to be in agreement with experimental data from 300° to 3000°K.