Charge Transfer in DNA
Photoinduced charge transfer in DNA occurs via two different hole-transfer mechanisms, diffusive hopping between sites with similar potential and tunneling over barriers with high potential. We discuss a simple kinetic scheme for diffusive motion and determine the stationary solution of the corresponding master equation. A continuous treatment leads to the diffusion equation. Hole tunneling appears over one or more bridge states and has to be described by a higher order superexchange mechanism. In general, both mechanisms are effective, dependent on the DNA sequence.