The Fine Structure of the Lineλ4686of Ionized Helium

Abstract

The fine structure of the line $\lambda 4686$ of ionized helium emitted from a discharge tube with hollow cathode cooled by liquid air was measured with a Fabry-Perot interferometer. The formula for the pattern obtained with this instrument expressed in Fourier series was applied in the analysis. Of the eight components predicted by theory, four were definitely observed, while the remaining weak ones were inferred from the pattern to be present. Relative intensities and positions of the eight components were found to be in general agreement with theory. The separation between the two strongest components was 0.0095±0.0024 IA or 0.4529±0.0109 ${\mathrm{cm}}^{-1\mathrm{}}$. The Rydberg constant for helium was calculated to be 109,722.430±0.030.