The series spectra of the stripped atoms of phosphorus (PV), sulphur (SVI), and chlorine (ClVII)

Spectra of stripped atoms, sodium to chlorine.—Grating spectrograms of order three to eight have been obtained of the hot-spark spectra of these elements, which have yielded more accurate values for the (3p2-3p1), (3s-3p2) and (3p1-3d) terms of AlIII, SiIV, PV and SVI, and have enabled the identification and determination within about 5 frequency units (1) of 18 series lines of PV, and thence of the 14 most important term values (3s to 6f′′), (2) of 11 series lines of SVI, and 10 corresponding term values (3s to 5f′), and (3) of the first doublet of the principal series of ClVII at 800.70 and 813.00 A. The position of this doublet was first predicted by use of the method developed in a previous paper(1), based on observed regularities in these spectra. Further evidence is presented for the fact that both the regular and the irregular doublet laws of x-ray spectra, hold also throughout the field of optics. A plot of sqrt[ν/R] for the stripped atom levels as a function of atomic number gives approximately straight lines (Moseley law), those for the 3s, 3p and 3d terms and for the 4s, 4p, 4d and 4f terms being approximately parallel (irregular doublet law). The doublet separations d1d2, however, do not fit well into the relativity doublet law, the ratio of observed to theoretical values decreasing from about .8 for SVI to less than .2 for SiIV, while AlIII and MgII are anomalous, d1 having a greater frequency than d2. The general similarity of the spectra of all these elements is strikingly shown in spectrograms on which appear the "D" doublet of Na and the corresponding "D" doublets of the stripped atoms of Mg, Al, Si, P, S, and Cl in the second, third, fourth, fifth, sixth and seventh ordelrs, respectively, all near 5600 A, that for Na being farthest from the mean position. The frequencies of all the known terms found for the stripped atoms of Na to S, are collected in a table. Ionization potentials of PV and SiVI, computed from the 3s levels of PV and SVI, come out 64.7 and 87.6 volts.