In this work, we discuss the effects of incomplete frequency redistribution on radiation trapping of the sodium D lines in laboratory experiments. We compare measured radiative escape factors from two recent experiments with values calculated from the Holstein theory, which assumes complete redistribution, and the Post theory, which explicitly takes into account both incomplete redistribution and the hyperfine structure of the atom. We show that the upturn of the escape factor vs density curve reported in the experiments of Romberg and Kunze is not a manifestation of the effects of incomplete redistribution. We also show that the data of Huennekens and Gallagher are more accurately fitted by a simple Holstein theory expression, where all effects of natural broadening on the lineshape are ignored, than by the more complete Post theory calculations. This is due to the fact that, in the present case, the density region where trapping is affected by incomplete frequency redistribution is small. Other recent experiments in mercury by Post and coworkers have demonstrated that such effects can be significant under different conditions. In addition, we present a calculation of Post's escape function η for an infinite slab geometry. This function is needed for Post theory calculations of escape factors and effective radiative rates in that geometry.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Quantitative Spectroscopy and Radiative Transfer|
|State||Published - Jun 1989|
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics