Extension of the Rh I-Like Isoelectronic Sequence to the Spectrum of Ag III

The spark spectrum of silver has been photographed and measured in the region from 500 to 3000A. To assist in the identification of Ag III lines, the spectrum of silver from the hollow cathode discharge in an atmosphere of helium was photographed from 500 to 2600A. A spark gap placed in series with the Schüler tube served to bring out the Ag III lines in the spectrum of this discharge. With the already reported separation of 4607 ${\mathrm{cm}}^{-1\mathrm{}}$ for the ground state, $4d^9{}_{}{}^2{}_{}{}^{}D_{2\frac{1}{2}, 1\frac{1}{2}}^{}{}_{}{}^{}$, as a basis and by employing the above method of distinguishing the radiations, it has been possible to establish 55 terms originating from the $4d^9$, $4d^{8}5s$, and $4d^{8}5p$ configurations and to classify a total of 257 lines. Approximate term values have been obtained by extrapolation of a Moseley diagram for the elements of this sequence. The value obtained for the lowest state of Ag III with respect to the $4d^8{}_{}{}^3{}_{}{}^{}F_4^{}{}_{}{}^{}$ state of Ag IV is 291,250 ${\mathrm{cm}}^{-1\mathrm{}}$, which corresponds to an ionization potential of 35.9 volts.