Scattering of polarized light in spectral lines with partial frequency redistribution - General redistribution matrix

The redistribution matrix for resonance scattering of arbitrarily polarized light, described by a vector of Stokes parameters, is derived assuming that the ground state is isotropic. When specified in the atomic rest frame, the redistribution matrix is found to be composed of several terms with individually separate frequency and angular dependence. The laboratory frame redistribution matrix exhibits an analogous structure, but the angular and frequency dependences are intermingled. Two possibilities for treating the angular dependence in practical applications are considered: an expansion in a series of Legendre polynomials and an azimuthal expansion. Finally, the concept of aximuthally average redistribution matrix is examined, and explicit expressions for resonance lines are given.