The absorption of light in cæsium vapour in the presence of helium

Abstract

In a recent paper we have described measurements of the absorption of light by cæsium vapour in the spectral region on the short wave-length side of the series limit. In the present work we examine the effect of the addition of a foreign gas on this absorption. Helium was used in a first investigation because, for reasons given below, we expected its effects to be simpler in interpretation than those of most other gases. Besides its intrinsic importance the work is of interest because a filling gas has been used to check the diffusion of the vapour in many experiments on absorption in metal vapours and the effect of these additional gases was quite unknown. Although helium has not been much used for this purpose, it seemed to be a suitable substance to use as a filling gas in future experiments.