Superexchange models

The quantum results (thick lines) of the sequential model (a) are seen to completely decay in the diabatic electronic ground state of the system. For short times, furthermore, the model predicts transient electronic population in the intermediate state. In the superexchange model (b), on the other hand, there is a nonvanishing long-time population of the initial diabatic state, whereas the intermediate state is hardly ever populated. We have performed classical mapping simulations with ZPE correction (a) y = 0.6 and (b) y = 0.34. The ZPE corrections have been calculated via Eq. (98) and are only employed to the... 

Electronic states of DNA fragments where the electron hole is located on a pyrimidine base are of high energy because cytosine and thymine are relatively weak hole acceptors [7, 51]. Nevertheless, the electronic coupling between nucleobases within (GC) and (AT) pairs may be of interest when one compares different CT paths in DNA using the superexchange model [14]. In Table 5, we present results of the electronic coupling within the base pairs (GC) and (AT) [41]. 

V(AiA2) instead of 0.0045 eV (Table 6), the GMH and FCD methods both give about 0.0030 eV. Furthermore, in [(CGi),(GC),(CG2)], the energy of the bridge (GC) is very close to those of the donor and acceptor sites, (CGi) and (CG2). Therefore, one cannot estimate V (GiG2) by a perturbation approach (superexchange model) or a related method [52, 54, 55]. Obviously, these systems cannot be reduced to a suitably coupled dimer when one considers coupling elements between nonadjacent sites. 

A superexchange model including many Cl states is possible by simple adaption of a calculational model such as CNDO/S to the excited states in a case of photo-induced ET [52], The advantage is that the treatment is more general than the simplified superexchange model of eq.(28). 

Ag is the variation of the g-tensor components from 2.0023. This interaction arises from the coupling of the paramagnetic moment to the lattice through spin-orbit coupling as was derived by Moriya by extending Anderson s superexchange model " to include the spin-orbit effect. 

The same series of Ru /Ru systems that were used to compare T,y values obtained from direct use of the MH model (Eq. 82) with the 7)/ values obtained from a superexchange model (Eq. 94), as discussed in Section 1.5.1, were also employed for a comparison of optical and thermal J)y values [135]. In this case the thermal T/y values were inferred indirectly from the estimated resonance-exchange component (AG() of the free energy change (AG, ) associated with the measured com-proportionation equilibrium between the 3-(-/3-(-, 2+/2+, and 2+/3+ oxidation states. According to the perturbative model adopted for the Robin/Day class-ll system [136], one obtains... 

The McConnell superexchange model is too simplistic for a protein intervening medium because of the complex array of bonded and nonbonded contacts between D and An important advance was made by... 

The value of p reflects the efficacy of the medium in coupling the donor and the acceptor. Since electronic coupling between donors and acceptors is often treated in terms of a superexchange model, the decay of electronic coupling is sometimes reported per bond rather than per unit distance. In the bond-coupling model, the exponent in Eq. 5 becomes [- P (A - l)/2]. 

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