Polarons hopping

This almost distance independent hole transfer over (A T)n sequences where adenines are charge carriers is very surprising. Maybe the transfer of a positive charge between adenines of an (A T)n sequence is extremely fast, as recent calculations of M.D. Sevilla predicted [20], One could also speculate that the positive charge is delocalized over more than one A T base pair so that polaron hopping, which is discussed in this volume by G.B. Schuster as well as E.N. Conwell, might make the hole transport in oxidized (A T)n sequences very efficient. 

Keywords Long-distance charge transport DNA damage Polaron hopping Ion gated base sequence effects... 

Schein LB, Glatz D, Scott JC (1990) Observation of the transition from adiabatic to nonadiabatic small polaron hopping in a molecularly doped polymer. Phys Rev Lett 65 472... 

Emin D (2008) Generalized adiabatic polaron hopping Meyer-Neldel compensation and Poole-Frenkel behavior. Phys Rev Lett 100 166602... 

The addition of Li20 to NiO leads to an increase in conductivity, as illustrated in Fig. 2.16. The lithium ion Li+ (74 pm) substitutes for the nickel ion Ni2+ (69 pm) and, if the mixture is fired under oxidizing conditions, for every added Li+ one Ni2+ is promoted to the Ni3+ state, the lost electron filling a state in the oxygen 2p valence band. The lattice now contains Ni2+ and Ni3+ ions on equivalent sites and is the model situation for conduction by polaron hopping , which is more often referred to simply as electron hopping . 

Although the mechanism of conduction in lithium-doped NiO and other low-mobility semiconductors is a controversial matter, the simple polaron hopping model outlined above serves well as a basis for understanding conduction processes in many of the systems discussed later (eg Section 4.4.1). 

Gill (1972) was the first to suggest that charge transport in polymers occurred by polaron hopping. The application of polaron theory to transport in polymers was first described by Sahvun (1984). Schein et al. (1990), and Schein (1992). The models described by Sahvun and Schein and coworkers lead to a mobility that is a product of a Boltzmann probability of energy coincidence and the probability a carrier will hop to an adjacent site by thermal activation once... 

Figure 28 The polaron hopping mobility versus reduced field for different degrees of off-diagonal disorder, assuming the absence of diagonal disorder.

Small-Polaron Hopping. The microscopic hopping mobility even among identical sites in the absence of disorder acquires an extra activation associated with the relaxation of the carrier and its polarized surroundings. 

For the activation-type small polaron hopping [2], /r is expressed as... 

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