Narrowing of Level-Crossing Signals by Radiative Transfer in Diffuse Reflection. I. Theory

Abstract

The multiple diffusion theory of Barrat has been extended by expanding the density matrix in irreducible tensors to calculate level-crossing signals arising from observation of the back-scattered light. In the framework of an approximation equivalent to the coherent scattering of radiative-transfer theory, we first calculate the different Hanle-effect signals, using, in particular, the results of Chandrasekhar which give light intensities in zero magnetic field. We then roughly evaluate the effect of the redistribution in frequency of the radiation and the variation of absorption with frequency. The narrowing predicted for the Hanle-effect curves is much less important than for lateral diffusion.