Interferometric wavelength measurements of forty-three germanium arc lines in the region from 4685 A to 2019 A have been performed. The light source used was a hollow cathode Schüler tube of special design employing a cast germanium cathode provided with a slot. The precision measurements carried out by means of a Fabry-Perot interferometer equipped with 6, 20, 36, and 49 mm spacers show that the germanium lines emitted by this source are of superior quality and merit use as secondary standards.
The measurements were employed for the establishment of precision values for one even energy level and for eighteen odd levels. Furthermore, by application of Ritz’s combination principle and by using the term analysis of the spectrum it was possible to calculate precisely the wavelength values of twenty-nine germanium lines in the vacuum region between λ1998 A and λ1691 A. These lines can be recommended as reliable standards in this wavelength region.
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