Some Higher Terms in the Spectrum of Ag II

The spectrum of silver has been excited in a hollow cathode discharge with a helium atmosphere. Wavelength measurements were made in the region from 500 to 2600A with a 1.5-meter grating vacuum spectrograph and in the region from 4000 to 11,000A with a Zeiss 3-prism spectrograph. Starting with terms already reported by previous workers as a basis, radiations have been classified sufficiently to establish the $4d^{9}6p {}_{}{}^{3, 1}{}_{}{}^{}\left(P^{\circ }{D}^{\circ }{F}^{\circ }\right)$ and the $4d^{9}7s$ and $8s {}_{}{}^{3, 1}{}_{}{}^{}D$ terms. A few terms of unknown origin have been found and in addition a few lines arising from the transition $4d^{9}5d$ to $4d^{9}5p$ have been identified. The application of a Ritz formula to the $4d^9\left({}_{}{}^2{}_{}{}^{}D_{2\frac{1}{2}}^{}{}_{}{}^{}\right)ns {}_{}{}^3{}_{}{}^{}D_3^{}{}_{}{}^{}$ series gives 134,110 ${\mathrm{cm}}^{-1\mathrm{}}$ for the limit of this series. The absolute value of the $4d^{10} {}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ term with respect to the $4d^9 {}_{}{}^2{}_{}{}^{}D_{2\frac{1}{2}}^{}{}_{}{}^{}$ level of the Ag III ion is thus found to be 173,274 ${\mathrm{cm}}^{-1\mathrm{}}$, which corresponds to an ionization potential of 21.4 volts.