Abstract
The relative fluorescence and/or phosphorescence yields of a number of methyl- and halogeno-quinolines, isoquinolines, and acridines have been measured as a function of the wavelength of the exciting light. In all cases the solvent was absolute ethanol. The results show that the efficiency of internal conversion processes between excited singlet states is extremely high in comparison to other intramolecular steps. The effect of substituted heavy atoms is discussed, as well as the fluorescence of the conjugate acids of the bases.