Polarized line transfer with F-state interference in a non-magnetic medium: Partial frequency redistribution effects in the collisionless regime

TL;DR

This paper extends the theory of polarized line transfer to include F-state interference effects in a non-magnetic, collisionless medium, analyzing how partial frequency redistribution influences the emergent polarized spectra.

Contribution

It develops a new redistribution matrix for F-state interference, incorporates it into the radiative transfer equation, and compares solution methods for polarized line transfer.

Findings

F-state interference significantly affects polarized line profiles.

The Neumann series expansion method is more efficient than PALI.

PRD effects alter the shape of the Stokes profiles.

Abstract

Quantum interference phenomena manifests itself in several ways in the polarized solar spectrum formed due to coherent scattering processes. One such effect arises due to interference between the fine structure (J) states giving rise to multiplets. Another effect is that which arises due to interference between the hyperfine structure (F) states. We extend the redistribution matrix derived for the J-state interference to the case of F-state interference. We then incorporate it into the polarized radiative transfer equation and solve it for isothermal constant property slab atmospheres. The relevant transfer equation is solved using a polarized approximate lambda iteration (PALI) technique based on operator perturbation. An alternative method derived from the Neumann series expansion is also proposed and is found to be relatively more efficient than the PALI method. The effects of PRD and the F-state interference on the shapes of the linearly polarized Stokes profiles are discussed. The emergent Stokes profiles are computed for hypothetical line transitions arising due to hyperfine structure splitting (HFS) of the upper J=3/2 and lower J=1/2 levels of a two-level atom model with nuclear spin I_s=3/2. We confine our attention to the non-magnetic scattering in the collisionless regime.