Computer simulation of decay kinetics of solitons and polarons in linear chain lattices

摘要

The diffusion-limited collisional decay process of solitons and polarons excited in a linear chain lattice is simulated numerically. The dependence of the survival function on the initial density and lattice disorder is examined. In the uniform chain, if the initial density N-0 is sufficiently low, the probability of solitons surviving at a time t agrees well with Torney and McConnell's solution S (zeta)=exp(8 zeta)erfc(8 zeta)(1/2), zeta=N(0)(2)Dt. for the unimolecular chemical reaction in a continuous medium, where D is the diffusion constant; the lattice effect appears with increasing N-0 as the slowing down of the initial decay. The survival probability of polarons is also given by a universal function S(zeta)=(1+33 zeta)(-1/4) within errors of +/-2%. As the lattice disorder evolves, S(S) transforms into the Kohlrausch law S(zeta) = exp{-(zeta/zeta(0))(beta)}. 0 < beta < 1, for both solitons and polarons, consistent with the experiment for long-lived photoexcited solitons in an MX chain compound. [References: 3]