Donor-acceptor molecular aggregates: Vibronic spectra of mixed Frenkel and charge-transfer excitons

We consider a linear stack of periodically arranged donor and acceptor molecules. Such a stack can carry Frenkel excitons (FEs) and charge-transfer excitons (CTEs). We study the case that the FE, excited at the donor, and the CTE, the hole of which is localized at the donor with the electron sitting at one of the neighboring acceptors, are transported through the stack, and that they interact among each other and with local vibrations at the donor and the acceptor. For this system we calculate the excitonic and one- as well as two-vibronic lines.