Abstract
Intensity variation at critical points in the helium spectrum.—Photographs of the helium spectrum produced in an equipotential space· using an equipotential cathode have been studied photometrically in order to determine the variation of line intensities on passing the various critical potentials. The results here reported cover the 54.2 volt point, at which double ionization is first possible. Spectra were taken at suitable values between 50 and 60 volts, often at intervals of 0.1 volt. The plates show a marked maximum of intensity near 54.2 volts for all lines measured.

This publication has 4 references indexed in Scilit: