Abstract
Theoretically calculated damping constants for the solar atmosphere at different optical depths, are compared with empirical values for three infrared multiplets of C i, O i and Si i resp. A test-calculation was also performed for the NaD-doublet broadened by a gas of He particles, for which many theoretical and experimental values are known.
In the case of neutral perturbers (H and He) we assumed that the interatomic potential was not a Van der Waals potential, but that a Smirnov-Roueff potential was the main cause of the line broadening. The latter description produces an enchancement of (γ H + γ He) with somewhat more than 20% in comparison with the pure Van der Waals assumption. Colliding electrons turn out to give a significant contribution γ e to the line broadening, especially towards the center of the solar disk (increasing values of the optical depth τ0). Using the Harvard Smithsonian Reference Atmosphere, assuming that the line broadening was caused almost solely by Van der Waals interaction and adopting abundance values A of Müller (1966), De Jager and Neven (1970) stated that the empirical values of Aγ were systematically larger than the theoretical ones, with factors ranging from 1.4 to 4.3. Using the same values for the abundance and the same model atmosphere we established the same discrepancy, but now with a factor ranging only from 0.8 (theoretical value somewhat higher than the empirical one) to 3.1. The discrepancy in the case of the C i multiplet (10700 Å) is almost completely removed. The calculations show further a decreament of γ with decreasing optical depth.
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Deridder, G., Van Rensbergen, W. Line broadening calculations for some infrared solar Fraunhofer lines. Sol Phys 34, 77–90 (1974). https://doi.org/10.1007/BF00149600
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DOI: https://doi.org/10.1007/BF00149600