Photometric investigations of alkali metals in hydrogen flame gases III. The source of the alkali metal continuum

When traces of alkali elements are present in the burnt gases of hydrogen + oxygen + nitrogen mixtures, a weak continuous emission, extending from the red into the near ultra-violet (ca. 3000 angstrom), is observed, in addition to some atomic lines of the alkalies. This continuum has been examined as a function of the nature and concentration of the additive, and of the temperature and composition of the flame gases. The observed small variation of the intensity of the continuum with temperature and the correlation of the intensity with the concentration of hydroxyl in the gases have led to the conclusion that the origin of the continuum lies in a radiative process A + OH $\rightarrow $ AOH + h$\nu $, where A represents an atom of alkali element. The results are not consistent with the previously held views that the continuum arises from a radiative recombination of oppositely charged particles. The possible use of the intensity of the continuum as a measure of concentration of hydroxyl is discussed.