Two-molecule systems exciplexes and excimers

Now consider two molecules, A and B, in such proximity that the electrons of one can interact with those of the other. For simplicity we shall confine ourselves to singlet energy levels, although many of the concepts that we shall explore are 

The various energy processes can be summarised on an extended Jablonski 

Two new phenomena can now occur. If the incident photon is absorbed by molecule A, it may be possible for the energy to undergo a resonance transfer to molecule B. 

The super script designates the electronic excited state of the molecule. This process will be attended by a diminution of the fluorescence from molecule A, and the appearance of fluorescence from molecule B. 

It may also be possible for the two molecules to form an excited state dimer. 

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