Collisional line broadening versus collisional depolarization: Similarities and differences |
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Authors: | S Sahal-Bréchot V Bommier |
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Institution: | 1. Laboratoire d’Étude du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris, UMR CNRS 8112, UPMC, 5 Place Jules Janssen, 92195 Meudon Cedex, France;2. Laboratoire d’Études Spatiales et d’Instrumentation en Astrophysique, Observatoire de Paris, UMR CNRS 8109, UPMC, UPD, 5 Place Jules Janssen, 92195 Meudon Cedex, France |
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Abstract: | Within the impact approximation, collisional line broadening parameters and depolarizing and polarization transfer (population, orientation, alignment transfer) rates are complementary: both include the effect of collisional transitions between the Zeeman sublevels of a given level, or between fine or hyperfine structure levels of a given term. However, there are several differences: in line broadening, the two levels connected by the radiative transition contribute to the broadening, and there is also an interference term between these two levels, whereas only one level or two close levels are concerned in the depolarization. Another difference lies in the fact that purely elastic collisions contribute also to the line broadening, whereas they do not contribute to the depolarization. The nature of these two kinds of coefficients are recalled. Then the possibility to find some relationships or systematic trends concerning depolarization versus collisional broadening is considered. This is to answer some current questions which come from the polarization community. |
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Keywords: | Collisional line broadening Atomic polarization Collisional depolarization |
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