On the self-quenching of the first excited singlet states of aromatic molecules in the gas phase

Abstract

The difficulty of interpretation of data on the variation in fluorescence yields of aromatic compounds in the gas phase as a function of pressure is pointed out, with particular emphasis on the effect of the geometry of the viewing system. Because of the non-obedience of Beer's law in such molecules it is shown that corrections to apparent quantum yields of fluorescence for geometrical effects based on optical density measurements are invalid. It is demonstrated that other methods may be used to determine the efficiency of self-quenching in these compounds, and that for three molecules which show a large variation in apparent fluorescence yield with pressure, selfquenching is not in fact important.