Principal and diffuse doublets of stripped atoms in five periods of the periodic table from Li I to O VI, Na I to Cl VII, K I to Mn VII, Rb I to Zr IV, and Cs I to Pr V.—Combining the data now available for the one-electron systems of the second, third, fourth, fifth and sixth periods certain regularities are found to exist between the successive elements in each period and between corresponding elements in successive periods. These regularities are found by the application of the regular and irregular doublet laws. For the long periods which involve more penetrating orbits extrapolations of $Z_i$ and $s_i$ (Landé's formula) prove to be better guides in identifying doublets of the higher members of a sequence although extrapolation of $s$ (Sommerfeld's formula) is entirely satisfactory for the sequences in the short periods. Using the former we have been led to correct our previous identifications of the principal doublet of Ce IV. The tighter binding of the $d$ electron over both the $s$ and $p$ electrons starting with Sc III, Yt III, and La III in the three long periods is especially well brought out by the Moseley type of diagram. Evidence is presented to indicate that the unexcited state of Ce IV involves a $5d$ rather than a $4f$ electron. New data are given for V V, Cr VI and La III.

• Received 31 October 1928

DOI:https://doi.org/10.1103/PhysRev.33.157