Towards proper parametrization in the exciton transfer and relaxation problem.: II.: Trimer

We extend our previous critical comparison of several parametrization schemes which have been used for transfer and relaxation of Frenkel exciton interacting with a responsive bath to the case of homogeneous cyclic trimer. Standard projection Formalism yields dynamic equations for the single-exciton density matrix rho complementing the usual single-exciton Liouville equation by adding terms describing the bath influence, The latter terms must, on the other hand, be properly parametrized. We found, mostly on the ground of analytical calculations which were allowed due to the simple structure of trimer, that the Redfield secular approximation could distort true time dependence of physical quantities calculated by means of exciton density matrix rho. (C) 2001 Elsevier Science B.V. All rights reserved.