Spectral Emissivity of Carbon Dioxide from 1800–2500 cm^−1*

Abstract

The spectral emissivity of carbon dioxide from 1800–2500 cm-1 is calculated as a function of temperature, pressure, and amount of radiating gas. Careful consideration is given to the choice of a proper model to represent the emission when the overlapping of the spectral lines is taken into account. At elevated temperatures the random Elsasser model should be used since many vibrational bands overlap. The emissivities were calculated from the usual intensity and energy expressions on an electronic computer taking into account up to 890 000 spectral lines at 2400°K. The electric moment matrix element was evaluated by using the harmonic oscillator approximation to represent the vibrational states. The emission from C13O2 and from the transitions near 2100 and 1900 cm-1 was included in the calculation. The shift of the emission to lower frequencies as the temperature increases is quantitatively explained. The emission in this frequency region from any flame can readily be obtained from the results given here.