| Presenter: | Moncef Derouich |
| Affiliation: | Institut d'Astrophysique Spatiale (IAS) |
| Title: | Effect of the anisotropic/isotropic collisions on the scattering polarization |
| Authors: | M. Derouich |
| Form: | talk |
| Abstract: | The contribution of anisotropic/isotropic collisions in the statistical equilibrium equations for the scattering polarization of multiterm atoms has not been treated before. This is unfortunate since some atomic systems in solar plasmas are realistically described in the framework of a multiterm case with hyperfine structure (e.g. Na~{\sc{i}}). In this talk, we intend to fill this lacuna. In addition, we establish the general expression of the (de)polarizing rates for the case of an arbitrary symmetry of the anisotropic collisions. From this general formula, we recover the limiting case of depolarization rates by isotropic collisions. We show the theoretical possibility of an alignment-to-orientation conversion mechanism by anisotropic collisions, leading to circular impact polarization emergence independently of the magnetic field strengths. It might be of interest to recall that, unlike electric dipole radiative transitions, collisional processes do not obey strong selection rules. On the other hand, we present our new results obtained for the depolarization rates of the levels of the CH molecule using different coupling schemes to treat the dynamics of collisions. These results allow us to study the variation of depolarization and polarization transfer rates as a function of rotational J-levels and temperature, and to make a comparison with our previous results concerned with the SiO molecule. |
| Session: | 5. Molecular polarization and collisional depolarization |
| Presentation date: | Wednesday 19th September |
| Presentation time: | 10:30:00 |