Towards proper parametrization in the exciton transfer and relaxation problem: dimer

We confront several parametrization schemes which have been used for transf er and relaxation of Frenkel exciton interacting with a responsive bath. St andard projection formalism yields dynamic equations for the single-exciton density matrix rho complementing the usual single-exciton Liouville equati on by adding terms describing the bath influence. The latter terms must, on the other hand, be properly parametrized. Using the simplest model systems , namely symmetric dimer in Part I and symmetric trimer in Part II, we foun d, that a usual parametrization scheme. called the Redfield secular approxi mation could distort true time dependence of physical quantities calculated by means of rho. (C) 2001 Elsevier Science B.V. All rights reserved.