Correlations between the components of stationary radiation in scattering media

Stationary radiation in a radiating, absorbing, and scattering medium is described by linear transport equations, which enables one to represent the radiation intensity as the sum of intensities, each of which is defined by its primary source of radiation and by the transmission of this radiation through the medium. In a scattering medium, the transmission depends on the characteristics of interaction between radiation and matter in the entire volume of the object. Fairly simple general correlations are derived between the intensity components that are independent of the concrete characteristics of the object. Previously, such correlations have only been derived for the case of heat radiation on the basis of the results of analysis of radiation equilibrium in a closed isothermal cavity. In the latter case, the correlations are derived from the condition of stationarity based on the analysis of the equation for the probability of complete disappearance of emerging radiation. The radiation may be arbitrary (it must not necessarily be heat radiation). The object may be of any shape and inhomogeneous. The surrounding walls may be both transparent and nontransparent. External lighting is possible. The correlations include quantities which are subjected to investigations in spectroscopic experiments. The use of the derived correlations in experiments with dust-laden plasma is described.