AuG. 19, 1923 MEGGERS: ARC SPECTRUM OF VANADIUM 319 
spectrum were first extended to the red and infra-red, and the analysis 
was practically complete when Cataldin’s'’ paper giving a partial 
explanation of both are and spark spectra of this element appeared. 
My efforts were then concentrated on vanadium, and in this paper 
some examples of the regularities in the arc spectrum of this element 
are presented. 
Wave-lengths of the spectral lines are taken from the measurements 
made by Ludwig,!® (2400 A to 4646 A), Kiess and Meggers!® (5500 
A to 9400 A), and Exner and Haschek,” the latter being corrected 
to the international scale. Arabic and Roman numerals following 
each wave-length refer respectively to the intensity and temperature 
class of the line. King! made a valuable study of the variation 
with temperature of the electric furnace spectrum of vanadium in the 
region 3165 A to 6842 A. In this interval the are intensities as 
estimated by King (loc. cit.) are used because he employed a larger 
scale (1 to 150) than the usual one (1 to 10) and made finer distinc- 
tions which are important in studying intensity rules governing lines 
of a multiplet. Under each wave-length is given the “frequency”’ 
or number of waves per cm. corrected to vacuum by the tables of 
Meggers and Peters.” The wave number differences or poly-fold 
level separations occurring in each group are given in italics between 
the connected pairs of lines. 
Tables of the are spectrum of vanadium contain about 2000 lines 
and about 15 per cent of these have now been assigned to multiplets. 
A few of the examples given below will require special study to settle 
doubtful points. For instance the lines 3184.00, 4384.73 and 4408.52 
may be double. The first of these appears in multiplet 14 and from 
King’s estimate of 60 for its intensity I have assumed it to consist of 
two lines of practically the same wave length and intensity. By so 
doing, the structure of the multiplet is completed and the distri- 
bution of intensity among its lines becomes normal. The same 
applies to multiplet 16 containing the line 4408.52 A to which King 
assigned the intensity 90. This work is still in progress, and a more 
detailed presentation and discussion of the results will appear later 
in the Scientific Papers of the Bureau of Standards. The evidence 
here given shows that vanadium falls into the general scheme, as 
17 Anales Soc. Espan. Fis. y Quim. 20: 606. 1922. 
18 Zeit. f. Wiss. Phot. 16: 157. 1917. 
19B. 8. Sci. Papers 16: 51. 1920. 
20 Kayser, Handbuch der Spektroscopie VI. 
* 21 Astroph. Journ. 41: 86. 1915. 
22 Bull. Bur. Standards 14: 697. 1918. 
