Influence of Temperature on the Concentration Quenching of Sensitized Phosphorescence of Organic Molecules in n-Paraffin Solutions

The sensitized phosphorescence of naphthalene and acenaphthene in frozen n-paraffin solutions (n-octane and n-decane) before and after their heating has been investigated. It has been established that heating of the frozen solution leads to an increase in the sensitized phosphorescence intensity. The influence of the solvent concentration on the above phenomenon has been analyzed. On the basis of the results obtained it has been concluded that the nonmonotone character of the temperature dependence of the sensitized phosphorescence intensity and its increase upon the sample heating are due to the removal of the concentration quenching in the process of solution annealing. It has been shown that in this case the intensity increases owing to the increase in the number of acceptor molecules participating in the radiation. The possible mechanisms of this phenomenon are discussed.