Wave-Lengths of Mercury 198

Abstract

The wave-lengths of 26 visible and ultraviolet radiations from H80198g have been measured to eight figures relative to 5460.7532A, provisionally adopted for the green line. A water-cooled electrodeless lamp containing two milligrams of artificial H80198g served as a light source when excited with radio waves of 100 Mc frequency. This lamp illuminated a Fabry-Perot interferometer and a large quartz spectrograph with which the interference patterns were photographed. Measurements of these patterns yielded relative wave-lengths with probable errors usually less than 0.0001A. In addition to demonstrating that H80198g 5460.7532A provides a practically perfect primary standard of length, this paper presents preliminary values of 27 superior spectroscopic standards which show that differences among vacuum wave numbers recur within the accuracy of the measurements, and that all the existing dispersion curves for air are incorrect.