Super-exchange energy

Next we shall show that the electronic energy transfer rate can be put into the spectral overlap form. Notice that by ignoring the super-exchange term we have... 

Exchange energy within super-paramagnetic crystals is sufficiently large to deal with the ensemble of electronic spins as with one large superspin S,... 

Super-exchange may play a considerable role in energy transfer especially in oxide host materials, however to our knowledge there is not enough experimental data and theoretical predictions at present to justify this assumption. 

There are many possible ways now for the energy to cross from P into P HL, including further dielectric relaxation. Table IV also shows that the state P BL is not lowered nearly as much, as the relaxation term is roughly proportional to the change in the dipole moment squared. These calculations do not support a direct role of this state in the charge transfer process, although we can not rule out the participation of this state in super-exchange [38,39]. 

The Dexter Mechanism This energy-transfer mechanism is possible in systems in which a spatial overlap, in terms of electronic structure, is present in the D-A dyad . Only in this case is electronic motion similar to super exchange possible, as depicted in Figure 13.12. 

Fig. 1. Nuclear potential energy curves for the parrallel sequential-superexchange mechanism. The super-exchange unistep occurs by the activationless crossing from the P BH curve (solid line) to the P+BH" curve (dashed line), while the first step (k ) in the two-step sequential process occurs (in the classical limit) by thermal activation on the P BH curve to its crossing with the P+B"H curve (dash-dotted line) followed by curve crossing. AG and AG are the free energy gaps between P bh and P+BH" and between P BH and P B H, respectively, while 5E is the vertical energy difference.

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