An Emission Coefficient (often indicated as j) is a measure of Electromagnetic Radiation (EMR) (e.g., light) Emission of a substance in a particular direction added to EMR passing through in that particular direction. They are used for modeling the effect of gas on passing EMR. It is a ratio of the EMR emitted to that entering the substance over a standard length through the substance. It will depend upon the substance and its density. It is the inverse of an Absorption Coefficient.
Equation of Radiative Transfer (RTE)
Source Function (S)