A Spectroscopic Determination ofem

Abstract

Rydberg constants for hydrogen and helium.—By an interferometer method the wave-lengths of the hydrogen lines at 6563A and 4861A were measured with reference to $\lambda 5015.6750$ of He as standard. The values so obtained were, for the doublet at 6563A, 6562.7110±.0018 and 6562.8473±.0009; and for the doublet at 4861, 4861.2800±.0013 and 4861.3578±0022. Similarly the wave-lengths of the 4686 lines of ionized helium were found to be 4685.7030±.0012 and 4685.8030±.0026. From these values of the wave-lengths the Rydberg constant for hydrogen, $R_{\mathrm{H}}$ is calculated to be 109,677.759±.008, and the Rydberg constant for helium, $R_{\mathrm{He}}$, to be 109, 722.403±.004.