Frenkel Excitons--Charge-Transfer Excitons--Phonons Coupling in One-Component Molecular Crystals

摘要

In this paper, we simulate the linear absorption spectra of the MePTCDI andPTCDA crystals. The basic Hamiltonian describes the Frenkel excitons andcharge-transfer excitons mixing in the molecular stack (point group C_i) andtheir linear coupling with one vibrational mode of an intramolecular vibration.Using the vibronic approach, we calculate the linear optical susceptibility inthe excitonic and one-phonon vibronic regions of the molecular stack and of acrystal with two types of nonequivalent stacks. We put the excitonic andvibrational parameters for the two crystals fitted in the previous studies andanalyze some important features of of the linear absorption lineshape in thespectral region of 15 000--23 000 cm^-1 and the virtual positions ofmany-particle bands. Our study exhibits the necessity of introducing theFE--CTEs mixing in the interpretation of the linear absorption spectra,especially in the MePTCDI crystal.