Line formation in spherical media with partial frequency redistribution. I - Solution of the line transfer

Abstract

The solution of line transfer with partial redistribution for an arbitrary (i.e., either stationary or moving) spherical medium is formulated in the framework of discrete space theory. The equation of line transfer for a two-level atom in spherical symmetry is solved for the case of isotropic scattering by using a source function and a line source function together with two angle-dependent and angle-averaged redistribution functions corresponding to zero natural line width and radiation damping with coherence in the atom's rest frame. Two pairs of reflection and transmission coefficients are obtained along with the source vectors, and results are examined for a static medium. It is found that large differences exist between the lines formed by complete and partial redistribution functions and that these differences persist in both spherically symmetric and plane-parallel geometries.