Knowledge Bank

“According to current theory of the phosphorescence of dyes, the rate of the decay of the emission should be directly proportional to the instantaneous number of excited, molecules. As in any first-order process, the intensity of the phosphorescence should therefore decrease with time following an exponential law. In the case of acriflavine, however, decay curves were found to deviate from the exponential decay law and the cause of this non-exponential decay has been the subject of many investigations and speculations. In previous investigations, however, the effect of physical state of the compound on the decay of phosphorescence has not been accurately assessed. Accordingly, the present investigation was conducted using the dye dispersed in rigid glass in the hope that the relatively simple physical system might allow more systematic study of the non-exponential decay of acriflavine. The effects of variation of several parameters, such as solvent, concentration, temperature and exciting wavelength on the decay of phosphorescence were studied. The significance of the results is discussed and a mechanism for the origin of non-exponential decay is proposed.”