Phenanthrene delayed fluorescence from

Fig. 25. Sensitized anti-Stokes delayed fluorescence from naphthalene.60 (1, 2) Delayed fluorescence from 10 "s3/ phenanthrene, and from mixture of phenanthrene (10"W) and naphthalene (3 X 10-3M), in ethanol. (3) Normal fluorescence from solutions 1 and 2 at 260 times less sensitivity. (4) Spectral distribution of exciting light for curves 1, 2, and 3, 0.7 X IQ-8 einstein liter"1 sec.-1 absorbed. (5, 6) Normal and delayed fluorescence from 3 X 10 lM naphthalene in ethanol excited by 313 m/i, 2 X 10-4 einstein liter-1 sec.-1 absorbed. Curve (5) at a sensitivity 100 times less than curve (6). Temperature for all curves was — 72° 3°C.

Parker CA, Hatchard C (1962) Delayed fluorescence from solutions of anthracene and phenanthrene. Proc Roy Soc Lond Ser A 269 574-584... 

The first observations of P-type delayed fluorescence arose from the photoluminescence of organic vapors.<15) It was reported that phenanthrene, anthracene, perylene, and pyrene vapors all exhibited two-component emission spectra. One of these was found to have a short lifetime characteristic of prompt fluorescence while the other was much longer lived. For phenanthrene it was observed that the ratio of the intensity of the longer lived emission to that of the total emission increased with increasing phenanthrene vapor... 

It has already been remarked that it is difficult to obtain reproducible values for the delayed fluorescence efficiency of phenanthrene from one solution to another. In ethanol, moderately high (though not reproducible) efficiencies have been observed but in highly purified n-hexane the efficiency was extremely low although anthracene gave similar results in both solvents. 

This phenomenon is possible in molecules like naphthalene, anthracene and Pyrene, each of which happens to have the lowest singlet energy level about twice hat of the respective triplet. For the generation of these triplets in high concentrations (T — T) type energy transfer from a suitable donor is necessary. Delayed fluorescence in naphthalene has been sensitized by phenanthrene. according to the following scheme ... 

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