Low Temperature Singlet Quenching Experiments by Heavy Atom-Containing Molecules: Anomalies in the Amount of Triplet-Triplet Absorption

Abstract

Addition of singlet quencher molecules like bromobenzene, ethyl iodide, and dimethyl mercury to degassed solutions of anthracene and phenanthrene in EPA at 77°K leads not only to a decrease in fluorescence measured in small glassy samples, but also to an abnormal decrease in the amount of triplet state absorption observed upon flash excitation of these solutions in large volume-containing low temperature cells. It is suggested that great care should be taken in order to be sure of the perfect homogeneity in the distribution of the quencher molecules throughout the sample investigated at low temperature. It is shown that the random distribution can hardly be attained, in view of the high concentration of quenching molecules needed in these experiments, when the cooling process is slow as is the case in a large volume-containing low temperature cell.