The line absorption spectra of the alkali metals

Abstract
The line absorption spectra of metallic vapours have become the subject of renewed experiment since the earlier empirical observations have been inter­preted in terms of the Bohr theory. Their chief importance now lies in the indication they afford of the character of the normal orbit of the “ valency ” or “ optical ” electrons in unexcited atoms, since such atoms can clearly absorb only those series for which this orbit determines the constant term. In this way the normal orbits have already been fixed for several groups of elements in the Periodic Table. The main features of the absorption spectra of the alkali metals were well-known long before the introduction of the Bohr theory. Wood and Bevan and other investigators had found that the principal series of the alkali metals are very readily developed in absorption; so readily that many more of the higher members of these series can be observed in this way than by any emission method. On the other hand, there is no absorption corres­ponding to the emission lines of the sharp or diffuse series. These facts together show that the outermost electron in these elements at the temperature used in the observations (200°-500° C.) must be present exclusively in the Is orbit. Sur and Ghosh (‘ Phil. Mag.,’ vol. 49, p. 60 (1925)) have recently found that at much higher temperatures a small proportion of the atoms are capable of absorbing the subordinate series lines, showing that their electrons have been expelled to an outer orbit by thermal excitation.

This publication has 0 references indexed in Scilit: