The Source Function in a NonEquilibrium Atmosphere. VIII. Solution for a Two Level Atom in a Finite Atmosphere.
Abstract
The solution for the variation with optical depth of the source function for a twolevel atom in a finite atmosphere, with and without temperature gradient, is presented. Even for an optical thickness of the atmosphere as high as tO , the emergent intensity differs by an order of magnitude from that for the semiinfinite case. For the case of nonsymmetric temperature gradient, the asymmetry in source function is very considerably less than for B (T ). The use of a model consisting of a finite slab isolated in space is a better approximation for such highexcitation ions as He ii, in a lowexcitation atmosphere such as the sun, than is the model of a semiinfinite atmosphere.
 Publication:

The Astrophysical Journal
 Pub Date:
 November 1961
 DOI:
 10.1086/147199
 Bibcode:
 1961ApJ...134..733T