Influence of solvent and intramolecular relaxation on dynamics of luminescence spectra in donor–acceptor complexes

Dynamics of luminescence spectra of photoexcited electron donor–acceptor complexes in a Debye solvent has been investigated within the Bixon–Jortner model. It has been shown that the main factors affecting the spectral dynamics in highly exergonic systems at times of up to several picoseconds are intramolecular vibrational relaxation in reactants and relaxation of solvent in the vicinity of an ion pair. Exact solutions of the mathematical model are obtained for two cases in which one relaxation channel dominates over another. The influence of the intramolecular reorganization energy on the luminescence-band profile at short times has been analyzed.