The Arc Spectrum of Germanium

Wave-lengths and classification of the lines of the Ge arc spectrum.—The wavelengths of lines in the germanium arc spectrum have been measured in the region above 1870A with an accuracy of at least 0.03A. From these lines the relative energy levels have been determined and transitions corresponding to 73 lines have been identified. In the normal state the germanium atom contains two $p$ valence electrons which give rise to the lower levels ${{}_{}{}^3{}_{}{}^{}P_{}^{\prime }{}_{}{}^{}}_{012}{}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$, with ${{}_{}{}^3{}_{}{}^{}P_{}^{\prime }{}_{}{}^{}}_0$ lying deepest as predicted by the theory of Hund. The next higher levels arise from the configurations $\mathrm{ps}$ and $\mathrm{pd}$. Data on the persistence of germanium lines were of great value in identification of the levels. At least two members of each of 11 series have been found and approximate limits have been calculated to be 65,300 for ${}_{}{}^2{}_{}{}^{}P_2^{}{}_{}{}^{}$ and 63,600 for ${}_{}{}^2{}_{}{}^{}P_1^{}{}_{}{}^{}$. The first resonance potential is 4.65 volts and the ionization potential determined by the limit ${}_{}{}^2{}_{}{}^{}P_1^{}{}_{}{}^{}$ is 7.85 volts. The similarities in the arc spectra of Si, Ge, Sn, and Pb are pointed out and the relative term values for these spectra are brought together in a single diagram.