On emission of radiation at the extremely far wing of a resonance line.

As it was experimentally shown earlier, there is an intense IR radiation in purely thermal emission spectra of dense sodium vapors. Based on the assumption that the wing profile is formed by buffer gas quasistatic broadening in nearest neighbor approximation, a theoretical model for the far wing of sodium D-lines was developed. The model described the experimental results within an order of magnitude, unlike to the standard theory of radiation transfer. However, the validity of this approximation at large detunings is not evident. Thus, the problem of the intense IR emission of dense vapors remains open. Its origin was also assigned to the influence of sodium clusters. In order to verify this hypothesis an investigation of absorption spectra of dense sodium vapors in a wide spectral range (0.35 - 1.1 µm) was carried out. For verification of the validity of the nearest neighbor approximation at large detunings, numerical calculations of the distribution function of ionic microfields in dense plasma were carried out. [ABSTRACT FROM AUTHOR]