Absorption spectra of iron, cobalt, and nickel

The underwater spark absorption spectra, as well as the ordinary vapor ab- sorptions, have been investigated by others, but not in sufficient detail in con- nection with the spectral structures of Fe, Co, and Ni. Employing high potential condensed sparks between electrodes of iron, cobalt, and nickel immersed in water, the underwater spark spectra of these metals were reexamined throughout the visible and ultra-violet regions. The spectrograms show 265 iron lines (2166 to 4404 A), 340 cobalt lines (2137 to 4121 A), and 225 nickel lines (2124 to 3858 A) absorbed in the source. In each case the majority of these are identical with the stronger lines of the arc-emission spectra, and practically all such lines are found to involve either the normal state or some low metastable state of the neutral atoms. These results confirm and extend the known spectral structures for neu- tral Fe, Co, and Ni; the normal states of these atoms are represented by 5 D, 4 F, and 3 F terms, respectively. The type of source used showed most of the metallic spark lines in emission, but certain groups were present in absorption with low intensity.