The broad depressions (2.6 A wide) in the solar spectrum at X 6362 and 6343 have recently been identified (Mitchell and Mohler, Astrophys. J. 141, 1126, 1965) as the auto-ionizing transitions 3d4p 3F0 -3d4d 3G in neutral calcium. A shock tube was used to determine the gf values of these lines and preliminary values have been derived. The McMath Solar Telescope at the Kift Peak National Observatory was used to observe these lines and to search for other broad absorptions. At the center of the disk, the depressions for the 6362 and 6343 A lines were 4.3~0.1% and 2.8*0.2%, respectively, while near the limb (~=0.2) the percentage depression decreased by 17%. Spectra of cool, highluminosity stars, kindly loaned by Mount Wilson and Palomar Observatories, also showed these auto-ionizing lines. Several other broad depressions which have been observed in the sun are discussed.
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Goldberg et al. (1965) studied this question.