Scattering polarization in the presence of magnetic and electric fields

Abstract

The polarization of radiation by scattering on an atom embedded in combined external quadrupole electric and uniform magnetic fields is studied theoretically. Limiting cases of scattering under Zeeman effect, and Hanle effect in weak magnetic fields are discussed. The theory is general enough to handle scattering in intermediate magnetic fields (Hanle-Zeeman effect) and for arbitrary orientation of magnetic field. The quadrupolar electric field produces asymmetric line shifts, and causes interesting level-crossing phenomena either in the absence of an ambient magnetic field, or in its presence. It is shown that the quadrupolar electric field produces an additional depolarization in the Q=I profiles and rotation of the plane of polarization in the U=I profile over and above that arising from magnetic field itself. This characteristic may have a diagnostic potential to detect steady-state and time-varying electric fields that surround radiating atoms in solar atmospheric layers. r

Polarization phase matrices for radiation scattering on atoms in external magnetic fields: The case of forbidden transitions in astrophysics

“…where ω = k, ω ′ = k ′ and J L (ω) denotes the reduced matrix elements for the atomic transition from a lower level to an upper level given by Eq. ( 31) of [31]. Further…”

“…These levels are characterized by states |Jm , where m denotes the magnetic quantum number which is projection of the total angular momentum operator J J J along B B B, which is taken along the Z−axis. If we consider atomic scattering J i → J → J f of radiation, the elements of the on-energy-shell transition matrix T are given [31,32] by…”

“…where T † denotes the hermitian conjugate of T considered as a 2×2 matrix with respect to the basis states of circular polarization. Following [31,32,33,34], the matrix elements for emission and absorption processes in Eq. ( 1) are given by…”

“…Therefore we focus our attention on scattering in the presence of magnetic fields. In our previous papers we developed a quantum electrodynamical (QED) approach to line scattering in the presence of external electric and magnetic fields of arbitrary strengths [31,32]. That approach can take account of all multipole type transitions, apart from the dominant one, namely, the dipole scattering.…”