Spectroscopic observation of recurrent phenomena in discharge tubes

Abstract

A method for the synchronous photography of irregular moving striations is described. It consists in forming an image of the positive column of a discharge along the slit of a spectrograph and covering and uncovering the latter with a mechanical shutter made to synchronize with the striations by a photoelectric device. The spectra obtained show variations in intensity along each line, corresponding to the intensity of the line in the bright and dark phases. Direct photography also of the actual striations is described. The photographs obtained for pure argon show that there is no appreciable recombination in the dark phase, while those for argon-mercury mixtures show excitation of only the mercury lines in the dark phase. These results have been explained by assuming that in the dark phase the electron energies are high enough to excite the mercury lines and are therefore too high to permit of recombination taking place. It is only in the bright phase that the energies are large enough to excite the argon lines. The optical results described are in accord with data obtained by Pupp by an electrical method. Their bearing on the work of Ladenburg is also discussed.