Wigner s rule

In contrast to the dipole-dipole interaction, the electron-exchange interaction is short ranged its rate decreases exponentially with the donor-acceptor distance (Dexter, 1953). This is expected since, for the electron exchange between D and A, respective orbital overlap would be needed. If the energy transfer is envisaged via an intermediate collision complex or an exciplex, D + A—(D-------A)- D + A, then Wigner s rule applies there must be a spin com-... 

Triplet-triplet annihilation can also occur by an exchange mechanism (according to Wigner s rules) ... 

In these reactions a close approach of two reacting partners is necessary. Essentially, Wigner s rule states that the total spins of the a type ( f)... 

The most important type of photosensitisation is governed by Wigner s rule, i.e., a triplet excited state produces another triplet and a singlet excited state produces another singlet... 

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