Certain Forbidden Spectral Lines of Cadmium*

Abstract

An experimental investigation was made to establish conclusively the source and nature of the highly forbidden lines 3320A×(5 1S0–5 3P00), 3141A(5 1S0–5 3P20), and 3403.1A(5 3P10–5 3D3) in cadmium. All such transitions are strictly forbidden for electric dipole radiation and by most of the selection rules for higher pole and magnetic dipole radiation. Bowen (see reference 1) and others, have suggested that the lines are emitted as the result of the interaction of the optical electron with the magnetic moment of the nucleus and are, therefore, produced by only the odd weighted isotopes.The intensities of the above mentioned lines as emitted by a cadmium sample which had been enriched in one of the odd isotopes were compared with the intensities of the same lines emitted by a sample of natural cadmium. Within the experimental error it was found that the forbidden lines are emitted with an intensity proportional to the odd isotope abundance and, therefore, it seems conclusively established that they arise only from the odd isotopes. Comparison of the intensities of some of the forbidden lines with the intensity of an allowed transition from the same multiplet was made in order to give a measure of the interaction of the optical electron with the nuclear magnetic moment.