Abstract:
The combined effect of partial frequency redistribution by atoms (PRD) and noncoherent electron scattering (NCES) on line formation is studied, taking account of the polarization state of the radiation field in resonance line scattering. For the purpose of comparison, a study is also made of redistribution by other mechanisms, namely complete redistribution and coherent scattering (CS) combined with NCES. A static medium stratified into plane-parallel homogeneous layers is considered. A conventional two-level atom approximation is employed as the basic model. The emergent linear polarization profile exhibits interesting characteristics in its variation across the line profile. Atomic redistribution plays an important role at the line core and the near wings of the resonance line. Electron scattering, however, makes significant contributions in the far wings (x is greater than 10). For resonance lines with high optical thickness, NCES leads to measurable changes of polarization in the far wings irrespective of the atomic scattering mechanism employed.
