Studies on Triplet Energy Transfer by Means of an Emission-Absorption Flash Technique. II. Mixed Triplet-Triplet Annihilation in Ethanol

Abstract

The mixed delayed fluorescence due to the processes, (Remark: Graphics omitted.) in the following systems in ethanol solutions have been quantitatively investigated, a) 1) 9-methylanthracene-anthracene, 2) 9-phenylanthracene-anthracene, 3) 9-methylanthracene-9-phenylanthracene, 4) anthracene-acridine, 5) 9-methylanthracene-acridine, 6) 9-phenylanthracene-acridine. b) 7) eosin-anthracene, 8) proflavine-anthracene, 9) eosin-acridine. It has been found that for class a) in which the separations of singlet excited levels of A and B are less than a few times of kT, the delayed fluorescence of both components occur and the value of (p_M^A+p_M^B is close to that of the efficiency of a simple p-type delayed fluorescence, p^A or p^B. The delayed mixed excimer fluorescence also occurs in most cases. For class b) in which the level differences largely exceed kT, only the delayed fluorescence of the lower level component occurs. It has also been established that the delayed excimer fluorescence in a single component system increases in intensity from anthracene through 9-methyl-to 9-phenylanthracene. The p_M^A/p_M^B values are discussed for systems (1), (2), and (3).