The Spectrum of Zinc Iv

The basic term structure in the third spark spectrum of zinc, Zn IV, is established herein for the first time. The spectral lines, excited in both sliding-spark and condensed-spark discharges in helium, were divided into their probable excitation classifications according to their behavior in these sources. Some 200 lines are classified as transitions between 17 even levels, arising from the configurations 3d9 and 3d84s, and 43 odd levels, arising from the configuration 3d84p. The analysis is shown to account for the principal Zn IV lines observed by Bloch and Bloch in the region λ < 500 Å, as well as our own data involving these and longer wavelengths. Comparisons made with the isoelectronic sequence Co I, Ni II, Cu III, and Zn IV show satisfactory agreement with anticipated regularities.