Intensity measurements in the helium spectrum

Abstract

The absolute and relative intensities of thirteen lines of the helium spectrum, extending through the visible region, have been measured by a modification of the method developed by Ornstein and Dorgelo. The change of the method has consisted in comparing each line directly with the known emission from a tungsten filament, operated under constant conditions. The results for a discharge in a capillary tube, with pressures from 1.92 to 34.3 mm show that the absolute intensities increase rapidly to a maximum for pressures in the neighborhood of 2 to 4 mm, below which they tend toward zero. The relative intensities of the singlet system are favored by lowered pressures, and the higher members of the triplet system are likewise favored over the lower members, while the relative intensities within the singlet series show little effect of pressure.