The Spectra of Cd IV, In V and Sn VI in the Isoelectric Sequence Rh I to Sn VI

The spectra of Cd IV, In V and Sn VI were photographed in the region 270A to 1800A with a three-meter, normal incidence, vacuum spectrograph, with a highly condensed, high voltage vacuum spark as a source of light. The irregular doublet law and the law of constant second difference were applied in the classification of many of the lines of these three ions. The separation of the $4d^9{}_{}{}^2{}_{}{}^{}D$ multiplet of the ground state has been found for all three ions. Most of the odd terms arising from the $4d^{8}5p$ electron configuration and some of the even terms arising from the $4d^{8}5s$ electron configuration have been determined. Classifications have been made for one hundred eighty-five lines of Cd IV, forty-three lines of In V and thirty-nine lines of Sn VI, making possible the assignment of fifty-one term values for Cd IV, thirty-two for In V and twenty-five for Sn VI.