Fluorescence and Photochemical Kinetics of Polyatomic Molecules in the Gas Phase

Various mechanisms for the excitation and quenching of fluorescence are discussed. It is pointed out that the classical Stern-Volmer mechanism may apparently be obeyed in cases where the process is not that of simple absorption followed by fluorescence and collisional deactivation. For polyatomic molecules a spectroscopic examination will not always disclose definitely the nature of the emitting radical or molecule. A study of the effects of several variables on the intensity of the fluorescence will frequently give much information about the lifetimes of the emitting molecules and the course of the photochemical reactions taking place. Quantitative studies of the fluorescence in the gas phase have been made for very few polyatomic molecules. Nitrogen dioxide and acetone are cited as examples.