On the Effect of an Electric Field and Gas Pressure on the Lines of Spectral Series

(M. Ritter. Ann. d. Phys. 1919, No. 10).

Stark bases the explanation of the broadening and displacement of spectral lines with increasing gas pressure on the following considerations: it is a known fact that spectral lines, under the action of a homogeneous electric field, split or, without splitting, are displaced toward longer wavelengths. Each element of the set of carriers of one or another spectral line in a gas is undoubtedly acted upon by the field of neighboring gas molecules (ions), and to varying degrees. This action is a function of the gas pressure, and therefore, with increasing pressure, there should be observed—if not a splitting of the spectral line—then its broadening and a displacement of the maximum of intensity.

In view of the scarcity of experimental material confirming these considerations, Stark proposed that Ritter take up the question of the parallelism between changes in spectral lines due to the action of an electric field and due to gas pressure. The question was investigated with the aid of the so-called Kathodenschichtmethode, developed by Stark, O. Hartke, and G. Libert in 1918, in an atmosphere of helium and argon with an admixture of nitrogen. The electric field strength in Ritter’s work was approximately \(26000 \frac{\mathrm{Volt}}{\mathrm{cm}}\).

The lines of zinc, mercury, lithium, and calcium were investigated. In all cases the expected parallelism was confirmed. Thus, in particular for zinc, Ritter found the following regularities:

a) The lines of the first triplet of the subordinate series of zinc, under the action of an electric field, do not split, but are displaced toward longer wavelengths.

b) The displacement of the components of one and the same triplet is approximately the same.

c) The broadening of the lines is asymmetric, and at the same time the fall of intensity toward longer wavelengths occurs more slowly than toward shorter ones.

Similar regularities were observed by Schwaim when the gas pressure was varied. Proceeding from Schwaim’s observations and his own on the line \(1\,N\) of zinc, Ritter gives for the field strength of the molecule a value of \(2080 \frac{\mathrm{Volt}}{\mathrm{cm}}\), which encompasses a region of radius \(8 \cdot 10^{-6}\,\mathrm{cm}\). Ritter considers his observations to prove Stark’s hypothesis unconditionally.

A. Predvoditelev.