Excimer fluorescence in polymers

It is known that a new component appears in the emission spectrum of many aromatic hydrocarbons with increasing concentration [147]. This new fluorescent component is ascribed to excimers which are complexes of an electronically excited molecule with an identical molecule in the ground state. In these complexes molecules are parallel at a distance of about 0.3 nm. Excimers only exist in the excited state after de-excitation the two partners repel each other. Therefore no corresponding change is observed in the absorption spectrum. The kinetic scheme just presented must be complemented by the following steps  

The over-all process of excimer formation, dissociation and deactivation is shown schematically in Fig. 34. 

The relative importance of normal and excimer fluorescence has been studied as a function of temperature with poly-1-vinylnaphthalene [156], 

In photo-stationary conditions the kinetic scheme for excimer formation and dissociation leads to [156, 158] 

Assuming ftFM and feFD to be independent of temperature, the occurrence of a minimum in the curve in Fig. 36 corresponds to the condition [158] that 

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