Observations on the Stark Effect in Hydrogen and Helium

Stark effect measurements for hydrogen and helium lines in fields 1 to 38 kv/cm.—The Lo Surdo method was improved by using a rotating cathode to minimize pitting. A three prism glass spectrograph, and a Hilger quartz spectrograph ${\mathrm{E}}_1$ were used. Enlargements of the spectrograms for $\mathrm{H}\gamma$ and for six He lines are given. (1) Hydrogen Balmer lines. At fields below 3 kv/cm, the red side of each line is more diffuse than the violet side, in agreement with Kramers' theory of the connection between the Stark effect components and the fine structure components. For fields above 5 kv/cm ten $p$ components of $\mathrm{H}\gamma$ are symmetrically arranged, the ratios of $\Delta \lambda$ to field coming out ±(.230,.191,.153,.065,.026) A/kv/cm. Changes in the relative intensities of components of $\mathrm{H}\gamma$ and of $\mathrm{H}\delta$ with increasing field are noted and the observed relative intensities of $\mathrm{H}\epsilon$ are found to agree fairly well with Kramers' theoretical predictions. (2) Parhelium lines. Measurements at five field strengths are given for the groups near the D lines 4388, 4144, 4009, and near $\lambda 3614$, including some new components. The number of lines in each group increases with the order. Combination series of the type $2P-mQ$, $2S-mQ (Q=S,P,B,E,F,\dots ;M=4,5,6,\dots )$ are suggested which include these lines and also the components of Stark's "diffuse principal" series and which fit into the scheme proposed by Tschulanowsky. The variable behavior of lines near $\lambda 4388$ in low fields is noted and observations are given for the $\lambda 3927$ group. As a rule the Stark effect pattern is constant for the members of each series but varies with the series. Many components vanish with increasing field. (3) Orthohelium lines. Measurements are given for groups $\lambda 3820$ and $\lambda 3705$ and observations for $\lambda 4026$.