THE INTENSITY AT THE BOTTOM OF THE FRAUNHOFER D LINES

Abstract
The line profiles were measured by scanning a photomultiplier and exit slit in the second order of a 21-ft. grating. The large distortions resulting from finite resolution were evaluated by means of an absorption cell containing sodium vapor with helium at a pressure of 170 mm. This produced an artificial line whose central intensity was known to be zero. By matching its profile carefully to that of the solar line the central intensities of D1 and D2 were found to be (5.0 ± 0.6)%and (4.8 ± 0.6)% in terms of the nearby continuum.