Electron incoherent hopping

Ishizaki A, Fleming GR (2009) Unified treatment of quantum coherent and incoherent hopping dynamics in electronic energy transfer reduced hierarchy equation approach. J Chem Phys 130 234111... 

The experiments just discussed made it clear that the motion of the hole on the series of As represents a different mechanism of transport than tunneling. Giese [13] and Bixon and Jortner [18] suggested that this mechanism is incoherent hopping of the hole between neighboring bases. This means that the hole wavefunction is Hmited to one base. The wavefunctions of the remaining electrons on that base would of course be distorted by the presence of the hole. Thus in this view of the transport process the base on which the hole sits could be called a molecular polaron, or a small polaron because it is limited to one site. 

The distance-dependence of the overall /q, may depart from that given by Eq. 90 due to additional distance-dependence arising from A or AC° [9, 119], or in cases of incoherent sequential electron hopping [19]. The role of the gap A, particularly in the quantity tjA, is seen to be crucial in controlling both the magnitude and distance dependence of Tjj. 

When the frontier orbitals of the bridge are not much higher in energy than those of D (for ET) or A (for HT), the dominant mechanism becomes incoherent charge hopping. Figure 4.16b shows ET by this mechanism. The electron hops in a thermally activated step from D onto the bridge frontier orbital(s) before it comes to rest on A. The intermediate state D B A is populated and the electron phase coherence is lost. The... 

For long distance electron transfer, thermal hopping or the incoherent mechanism dominates. In this case, the electron is localized on the molecule and moves in a series of steps. Evidence for this mechanism in DNA duplexes comes from the experiments of Nakatani et al. [111]. 

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