The Hydrogen Doublet

IN measuring doublet separations, the Fabry-Perot interferometer can be so adjusted that the fringes of one component fall half-way between those of the other. This eliminates most of the distortion present in other instruments. Using this method, the doublet separations at a pressure of 0.5 mm. and a current density of 0.25 amp. per sq. cm. have been found to be 0.316+/-0.002 for Hα, 0.329+/-0.005 for Hβ, and 0.353+/-0.007 for Hγ. The wave-lengths of each component have also been determined and indicate that R = 109677.70+/- 0.04, with the use of Sommerfeld's formula.