Excitation resonance interaction

The nature of the bonding in these excited state complexes has been the subject of several theoretical studies recently reviewed by Blrks (4). The first theoretical approaches, based on charge resonance and excitation resonance Interaction, were not completely successful. Konijnenberg (8) proposed a combined model of configuration Interaction between charge resonance and excitation resonance states. In heteroexcimers or exciplexes, excitation resonance is impossible because of the difference in... 

The physical processes of absorption, refraction, circular dichroism and optical rotatory dispersion are closely inter-related, such that mechanistic discussions of the latter two require adequate consideration of the former two. Accordingly, this presentation begins with consideration of basic elements and terminologies of absorption and refraction, and then treats circular dichroism and optical rotatory dispersion, and in so doing provides prosthetic group examples of excitation resonance interaction and of the dispersion force interactions giving rise to hyper- and... 

For dilute solutions of essentially independent donor and acceptor molecules the Forster or resonance interaction is quite important in molecular aggregrates and in molecular crystals exciton interactions are likely to be important. When the interaction is strong the excitation is not localized on the donor or acceptor but is spread over both. If larger aggregrates are involved, the excitation can be spread over many molecules/33-3 This can easily be seen for the case of a dimer where the donor and acceptor are... 

Complex formation is important in photophysics. Two terms need to be described here first, an exciplex, which is an excited state complex formed between two different kinds of molecules, one that is excited and the other that is in its grown state second, an excimer, which is similar to exciplex except that the complex is formed between like molecules. Here, we will focus on excimer complexes that form between two like polymer chains or within the same polymer chain. Such complexes are often formed between two aromatic structures. Resonance interactions between aromatic structures, such as two phenyl rings in PS, give a weak intermolecular force formed from attractions between the pi-electrons of the two aromatic entities. Excimers involving such aromatic structures give strong fluorescence. 

Next we model the laser-driven electron dynamics quantum mechanically to reveal analogies and differences to the simple classical model. In view of the SPODS mechanism, which is based on resonant interactions, we consider only two quantum states at hrst, the ground state and the resonantly excited state. Eor this purpose, we briehy recapitulate the relevant equations for a two-state system driven on... 

In the Forster mechanism, the energy transfer upon excitation may take place between excited molecular entities separated by distances R, which are considered as spatially fixed Frenkel excitons. It is described in terms of resonant interaction between their transition dipole moments, which decreases as Rr6. 

R. D. Harcourt, G. D. Scholes and K. P. Ghiggino, Rate expressions for excitation transfer. II. Electronic considerations of direct and through-configuration exciton resonance interactions, J. Chem. Phys., 101 (1994) 10521-10525. 

Figure 25. Diagrammatic representation for a system with two chromophores (A and B) held together by covalent bonding or weak intermolecular forces. Local excitations are shown (left and right) for the chromophores in their locally excited (A or B ) monomer states. In the composite molecule or system (center), excitation is delocalized between the two chromophores and the excited state (exciton) is split by resonance interaction of the local excitations. Exciton coupling may take place between identical chromophores (A=B) or non-identical chromophores (A B) but is less effective when the excitation energies are very different, i.e. when the relevant UV-visible bands do not overlap.

An assembly of molecules, weakly interacting in a condensed phase, has the general features of an oriented gas system, showing spectral properties similar to those of the constitutive molecules, modulated by new collective and cooperative intrinsic phenomena due to the coherent dynamics of the molecular excitations. These phenomena emerge mainly from the resonant interactions of the molecular excitations, which have to obey the lattice symmetry (with edge boundary, dimensionality, internal radiation, and relativistic conditions), with couplings to the phonon field and to the free radiation field. 

Photoredox processes include both photoreduction and photo-oxidation of the excited species. An electron transfer that results from an electronic state produced by the resonant interaction of electromagnetic radiation with matter is called photoinduced electron transfer (PET) [30-32]. This can be done by either a direct or a photosensitized process (see below and Figure 6.6). 

The distribution parameter a reflects the root-mean square standard deviation of the non-resonance interaction energy D [cf. Eq. (13)] corresponding to the polarization energy of a charge carrier in a medium (cf. Sec. 2.3.1). The essential contribution to D is the difference of the van der Waals energies between an unexcited and excited molecule embedded in a medium of polarizability a. 

If the light emanating from an organic LED originates from the radiative decay of locally excited (molecular) states (see Fig. 11), we deal with molecular emission spectra. They, in general, differ from those of isolated molecules because the gas-to-solid shift, and resonance interactions must be taken into account [cf. Eq. (13)]. Moreover, they can reveal wider bands due to dynamical and structural disorder in the solid... 

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