Time and frequency resolved emission spectra of a single molecule or a supramolecular complex (SC) placed in the vicinity of a metal nanoparticle (MNP) were computed in the framework of a novel theory. In order to focus on the subwavelength extension of the whole system, the molecule-MNP coupling was restricted to the instantaneous Coulomb-interaction. Its nonperturbative consideration achieved in a density matrix description strongly affected the photon emission but allowed to treat the coupling to transversal photons in perturbation theory. For the single molecule-MNP system a vibrational coordinate was included to describe respective effects of molecular electron-vibrational coupling. When studying an SC interacting with a MNP, intermolecular excitation energy exchange coupling and energy transfer were considered. Respective time and frequency resolved emission spectra were presented. They showed a strong enhancement when compared with the case where the MNP was absent. Furthermore, the emission offered parts of the molecular energy spectra otherwise not visible.
Excitation energy transfer (EET) in molecular systems is studied theoretically. Chromophore complexes are
considered which are formed by a butanediamine dendrimer with four pheophorbide-a molecules. To achieve
a description with an atomic resolution and to account for the effect of an ethanol solvent a mixed quantum
classical methodology is utilized. Details of the EET and spectra of transient anisotropy showing signatures of
EET are presented. A particular control of intermolecular EET is achieved by surface plasmons of nearby placed
metal nanoparticles (MNP). To attain a quantum description of the molecule-MNP system a microscopic theory
is introduced. As a particular application surface plasmon affected absorption spectra of molecular complexes
placed in the proximity of a spherical MNP are discussed.
Ultrafast heterogeneous electron transfer (HET) between a molecule attached to a semiconductor nanocluster
and the band states of the cluster is discussed theoretically with emphasis on the perylene TiO2 system.
The whole approach has been formulated in such a way to be ready to describe different optical excitation
and detection processes. Therefore, a model is introduced which accounts for the specialty of the molecule
i.e. its particular electronic level scheme together with its vibrational degrees of freedom as well as the band
continuum of the semiconductor. Calculations of the steady state linear absorption spectra are used to adjust
the parameters of perylene attached to nano-structured TiO2 via different bridge-anchor groups. These data
are used to compute the temporal evolution of the energetic distribution of the injected electron. Finally, it is
demonstrated that a two-photon photon emission spectrum carries signatures of the molecular vibrations.
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