Intensities in the helium spectrum

Abstract

Merton and Nicholson made a quantitative study of the distribution of intensities in the spectra of hydrogen and helium under different conditions. Among other things, they studied the distribution of intensities in the helium spectrum as a function of the distance from a flat cathode in a wide vacuum tube. They also investigated the effect of admixture of other gases, and the effect of putting a condenser in parallel with a vacuum tube. The results were extremely interesting; but it seems that, in most cases, the changes were brought about by a simultaneous change in more than one variable, or that they were changes of a kind not capable of simple specification in terms of atomic processes. Thus when a condenser is put in parallel with a vacuum tube, the energy of impact of the electron on the atom and the density of the current are altered. Moreover, both of these vary rapidly with the time, since the current is necessarily alternating. To account for the observed distribution of intensities under such conditions is a formidable problem when we consider that the quantitative explanation of the intensity of any spectrum line would be a different problem, on any atomic theory, even when the conditions are reduced to the very simplest.