Anthracene, absorption spectrum delayed fluorescence

Fig. 17. Delayed fluorescence spectrum of 5 X 10-63/ anthracene in ethanol.84 Half-bandwidth of analyzing monochromator was 0.05 ju-1 at 2.5 n K Intensity of exciting light was approximately 1.4 X 10 einstein cm. a sec.-1 at 2.73m-1 (366 mju). (1) Normal fluorescence spectrum (distorted by self-absorption). (2) Delayed emission spectrum at sensitivity 260 times greater than for curve 1. (3) Spectral sensitivity of instrument (units of quanta and frequency).

No difference in the absorption spectrum is observed. The lifetimes of the two fluorescence emissions are both of the order of 10-8 sec. Another effect has been observed with hydrocarbons both as vapor and in solution, namely, a "delayed fluorescence emission with a life of a few milliseconds (56,63). This was at first interpreted as process 9, and the term excimer applied to the hypothetical excited dimer. However, C. A. Parker and C. G. Hatchard have shown that the intensity of the delayed fluorescence, which has the same spectrum as that from the excited singlet molecule, depends upon the square of the intensity of the exciting light (49). The mean life of the delayed fluorescence of anthracene solutions is (about) one-half that of the triplet state, and the effect is not observed in rigid media. These facts show that the delayed emission must be caused by an interaction between two triplet-state molecules ... 

An observation of the triplet state of anthracene in benzene (27) is of special interest in that, in addition to the absorption spectrum of the triplet, a delayed fluorescence emission from the singlet at 4300 A. was recorded. The intensity of fluorescence, which was approximately proportional to the square of the triplet concentration at all times, was attributed to triplet-triplet quenching ... 

Fig. 6.1 The Davydov splitting Aq = 21.5 cm of the 0.0-transition in the T] So absorption spectrum of anthracene at 300 K. This is the excitation spectrum of the triplet excitons. The absorption was detected via the intensity of the delayed fluorescence...

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