title: Three-pulse photon echo of an excitonic dimer modeled via Redfield theory.
abstract: In this article the third-order response of an excitonically coupled dimer is studied. The three-pulse photon echo signals were calculated by extracting polarization components from the total polarization in the corresponding phase-matched directions. The total nonlinear response was obtained by numeric propagation of the density matrix, with the exciton-vibrational coupling modeled via Redfield relaxation theory. The full two-dimensional three-pulse photon echo signals and the peak shift were analyzed in terms of the density-matrix dynamics of coherence dephasing and population relaxation. The location of the two-exciton state was found to be essential for proper modeling of the three-pulse photon echo. In particular, an oscillation in the three-pulse photon echo peak shift is found if the two-exciton state is displaced. The oscillations can be related to the dynamics of the one-exciton coherences.
authors.affiliation: Department of Chemical Physics, Lund University, Box 124, 22100 Lund, Sweden.
authors.forename: Pär
authors.initials: P
authors.lastname: Kjellberg
authors.forename: Tõnu
authors.initials: T
authors.lastname: Pullerits