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Physics LibreTexts

4.8: Emission Coefficient

This is the intensity emitted per unit volume of a gas. In this definition, the word “intensity” (without being preceded by the word “specific”) is intended to mean what is meant in section 1.4. The symbol used for emission coefficient is \(j\), and the SI units are \(\text{W sr}^{-1} \ \text{m}^{-3}\).

The mass emission coefficient \(j_m\) is the intensity per unit mass, and is related to the volume emission coefficient by \(j = \rho j_m\). Not all authors are equally clear as to whether they are referring to a volume or a mass emission coefficient.