Stark patterns observed in helium

Abstract

This paper is mainly a report of further observations on the Stark-effect in helium made with a view to establishing various definite Stark patterns for the series lines. It thus appears as an extension to an earlier paper in which it was pointed out that a plan for Stark patterns is contained implicitly in the Bohr perturbation theory of the Stark-effect as developed by Kramers to predict connections between the hydrogen fine structure and the components observed in high fields. This plan, which on the perturbation theory might be expected to make its appearance in helium, receives somewhat detailed support from the present data, and will be outlined in later paragraphs. It should be stated now, however, that while the detailed analyses here given may be regarded as an extension to the observations by Stark and Nyquist, they offer definite reasons for a rather extensive revision of the complex analyses reported by Takamine and Kokubu. Soon after his discovery of this effect Stark suggested that it might be found to be of the same nature for the various members of a single spectral series. He noted, in particular, that on the early plates certain principal and sharp series lines of helium were merely displaced without being split by the applied electric field. In the following paper Stark and Kirschbaum gave the results of a more complete examination of the Stark-effect for the series lines of orthohelium, parhelium, lithium, and the doublets of calcium. With the single exception of the parhelium line λ 3614, which appeared to be double, they found all principal and sharp series lines simply displaced. The two components of each calcium doublet were shifted in the same direction, and by nearly the same amounts.