Absorption Spectra of the Palladium and Platinum Triads

Under certain conditions the continuous spectrum from high potential sparks between metal electrodes immersed in a liquid is interrupted by absorption lines which are identifiable with lines in the arc emission spectrum of the metal. The importance of these lines lies in the fact that in numerous cases where the spectral structures are known, they have been shown to involve the normal state and sometimes low metastable states of the atoms. By extending these observations to unclassified spectra, this method thus permits the identification of the low levels in the spectral structures.Using electrodes of Ru, Rh, Pd, Os, Ir, and Pt, in the under-water spark, the absorption spectra of these metals were determined down to wave-lengths near 2000A. Analyses of these data reveal the low levels in the arc spectra of the Pd and Pt triads as follows: the lowest energy is represented by a quintet-F term for Ru, by a quartet-F for Rh and by a singlet-S for Pd. A considerable number of the absorption lines for Os, Ir, and Pt have been classified with levels but it is impossible at the present time to recognize their spectral types, except that for Ir the lowest level is probably a doublet-D term and for Pt it is probably a triplet-D. The quantum-theoretical arrangement of low levels as derived from the electron configurations in these atoms is summarized.