Molecular Hanle effect in the Paschen-Back regime

¹ Institute of Astronomy, ETH Zurich, 8092 Zurich, Switzerland e-mail: shapiro@astro.phys.ethz.ch
² Astronomy Division, PO Box 3000, 90014 University of Oulu, Finland
³ Faculty of Mathematics & Science, University of Zurich, Germany

Received: 13 July 2006
Accepted: 23 September 2006

Abstract

Context.The second solar spectrum resulting from coherent scattering is a main tool for diagnostics of turbulent magnetic fields on the Sun. Scattering on diatomic molecules plays an important role in forming this spectrum and even dominates in some spectral regions.

Aims.In a magnetic field electronic states of a molecule are often perturbed via the Paschen-Back effect. Sometimes this perturbation can completely change the spectrum, not only quantitatively, but even qualitatively. Here we calculate molecular scattering properties taking into account the Paschen-Back effect.

Methods.Starting with the Hund's case (a) wave functions as a basis we obtain with the perturbation theory wave functions of the intermediate Hund's case (a-b) in a magnetic field. Using new, perturbed values of the Landé factors and transition amplitudes we calculate the Mueller matrix for coherent scattering at diatomic molecules in the intermediate Hund's case (a-b) and look for the effects that can be caused by the Paschen-Back effect.

Results.We have found a considerable deviation from the Zeeman regime and discuss here the quantitative and qualitative effects on observed polarization signals for the CN  and MgH systems as examples.