New Features of the Red Band System of Sodium

Abstract

The occurrence of an infra-red edge to the red band system of ${\mathrm{Na}}_2$ is reported and is explained in terms of the Franck-Condon theory of intensity distribution when account is taken of the shape of the potential energy curves as dissociation is approached. The same theory explains a head of the red system in the yellow-green, the reappearance of the orange "cathode-ray fluorescence" series in the infra-red, and the observed asymmetry in the two branches of the Condon "parabola."