Intensity measurements in a fine structure multiplet of As II

Abstract

The present work was undertaken with the object of testing the fine structure intensity formulæ deduced by Hill. Up to the present very few intensity measurements have been made on the fine structures arising from nuclear spin. The principal difficulty in such measurements arises from the smallness of the structures which are usually incompletely resolved by the interferometers employed. The use of the interferometer in any event necessitates careful corrections for the instrumental intensity distribution. Schüler and Keyston have made photometric determinations of the intensity ratios in the fine structures of two Cdl lines and have verified the intensity rules for these lines. An inherent difficulty in the examination with a FabryPerot interferometer of Cdl structures lies in the presence of an intense evei isotope line within the pattern due to the nuclear spin of the odd isotopes The even isotope component contributes 77% of the intensity of the line and the remaining 23% is distributed amongst the members of the nuclear spin multiplet. The authors do not describe their method of coping with this difficulty which, judging from the experience of the present writers, must have been serious.