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The theoretical strengths of the diffuse triplet lines of He r have been employed in connection with Menzel and Cillié's measures of 1932 chromospheric lines in an attempt to determine the excitation temperature of the solar chromosphere. The temperature appears to increase with the height, ranging from 4300° for the chromospheric slab 670 km above the solar limb to 6700° for a height of 2330 km. The diffuse singlet lines of He i appear to be anomalously faint relative to the dif- fuse triplets. The suggestion is made that, in a rarefied chromosphere, the combination of the metastabffity of the 2~S level and a possible excess of ultraviolet radiation in the region at 500 A may account for the relative faintness of the singlets
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Leo Goldberg (1939) studied this question.
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