Calculation of absorption line shape based on reduced density matrix approach

COMP 212

Mino Yang,, Department of Chemistry, Chungbuk National University, Cheongju, 361-763, South Korea
A theory for the line shape of molecular aggregates is formulated based on the reduced density matrix. Electronic coupling between the molecules is assumed to be weak. The spin-Boson model is introduced to include the effect of electron-phonon coupling. We derive kinetic equations for the reduced electronic density matrix associated with the absorption spectrum. General expressions of the time-dependent rate constants in the kinetic equations are derived by use of the cumulant expansion technique. The resulting time-dependent kinetic equations are solved numerically. We illustrate the applicability of the present theory by calculating the line shape of a dimer.