Empirical Investigation on the Impact of Hydrogen Collisions for the Formation of CI 1.07 mu~m Lines Based on the Solar Center-to-Limb Variation

摘要

With an aim of examining the validity of non-LTE line-formation calculationsfor the strong C I lines of multiplet 1 at 1.068-1.069 mu~m, especially interms of the treatment of collisions with neutral hydrogen (H I) atoms, wecomputed theoretical equivalent widths (W_lambda) of these lines correspondingto specific intensities of different angles (mu = cos(theta)) on the solar diskunder various conditions, which were then compared with the empirical W_lambdavs. mu relations obtained from our spectroscopic observations using theDomeless Solar Telescope at Hida Observatory. It turned out that ourobservational data are almost consistent with the theoretical simulations donewith the H I collision rates computed with the classical formula, whichsuggests that the necessity of its significant revision (e.g., considerablereduction) is unlikely.