The asymmetry of the H? absorption coefficient

Abstract

Because of fine structure splitting and Lamb shift the seven lines of the Hα transition array do not fall together. The separation between the most intensive components amounts to 0.14 A, a value which is comparable with the Doppler width representative of the layers where the solar Hα pro-file originates. Inclusion of this splitting in the line absorption coefficient leads to a better agreement between computed and observed profiles. The transfer problem needs not be solved for each of the seven lines, because the very intensive collisionally-induced term-term transition rates ensure the redistribution of the populations among the levels according to their degree of degeneracy. The Harvard Smithsonian Reference Atmosphere yields profiles which agree rather well with observations, the very line centre excepted. The new characteristic of these profiles is their asymmetry: the centre of symmetry of the line wings is not equal to that of the line core.