Early investigations in the spectra of Pb IV by Rao and Narayan, Smith and Kishen have been extended to include 34 terms arising from the configurations $5d^{10}\mathrm{ns}$, $5d^{10}\mathrm{np}$, $5d^{10}\mathrm{nd}$, $5d^{10}5f$, $5d^{9}6s^2$, $5d^{9}6s6p$ and $5d^{9}6s6d$. With data by Arvidsson, Smith and the author, the region reported extends from 198 to 5005A and 79 lines have been classified. In the extension to Bi V, values have been assigned to 14 terms involving 18 lines in the region below 1487A. By a Hick's formula the value of the $5d^{10}6s {}_{}{}^2{}_{}{}^{}S_{0\frac{1}{2}}^{}{}_{}{}^{}$ term has been computed to be 340,885 ${\mathrm{cm}}^{-1\mathrm{}}$ for Pb IV and 451,700 ${\mathrm{cm}}^{-1\mathrm{}}$ for Bi V, giving ionization potentials of 42.0 and 55.7 volts, respectively.

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