Intensity measurements in the secondary spectrum of hydrogen

Abstract

Prof. McLennan and others have published in these Proceedings a paper in which they have given results of their measurements of the intensities in the secondary spectrum of hydrogen. The experimental results mentioned in the tables of that paper, however, are only densities, and no attempt was made to find from those densities the real values of intensity in the spectrum. The relations between density and intensity, however, is not so simple as McLennan supposes, as is shown in fig. 1 which follows this. In this paper it will be shown that for theoretical investigations on the secondary spectrum it would be dangerous to use the figures given by McLennan. We shall do this at the moment for a region from 4500-4900 Å.; the real intensities in this region will be shown to differ considerably from those given by McLennan. The intensities of about 230 lines have been measured by the method developed in our Institute. Further, our work shows that the source of error, already mentioned by McLennan— e. g . (p. 281), the difference of sensitivity of photographic plates in this region—can be considerable. Fig. 2 represents the sensitivity as a function of wave-length for the plates used (Ilford Special Rapid). Measurements for other regions of the secondary spectrum will be published soon. The application of the intensity rules is hardly possible at present, as the number of lines of which the classification is certain is too small, and also the wave-lengths are not known with sufficient accuracy. In this paper we give, in addition to the measurements of intensities, the wave-lengths of a number of complex lines not described or uncertain in existing literature.