Chromophore couplings

Besides the single chromophore PES lJmg, this expression includes inter chromophore couplings Jmn describing the Coulomb-interaction among the different unexcited chromophores. They are the electronic ground-state variant of the general expression... 

The inter chromophore couplings are reduced here to a simple electrostatic coupling among the charge distribution of the electrons and nuclei in chromophore m and n. It appears if the electron charge and that of the nuclei are... 

For comparison we present the absorption cross section for the case where inter-chromophore coupling can be neglected and where the use of the Condon-approximation becomes possible. We arrive at... 

We consider an approximate expression for the emission spectrum. It neglects inter-chromophore coupling, assumes that the Condon-approximation can be carried out, and considers the case of fast vibrational relaxation in the excited electronic state of the individual chromophores ... 

Fig. 6. Measurement of photostability of two polymeric electro-optic materials as carried out by researchers at IPITEK (TACAN) Corporation. The data represented by the solid line correspond to the LRD-3 DEC material of Dalton and co-workers [138] while the data represented by open circles correspond to a diaminonitrostilbene chromophore/poly(methyl methacrylate) guest/host material produced by IBM Almaden Laboratories. The dramatic improvement observed for the DEC material can be associated with increased lattice hardness from the chromophore coupling to adjacent polymer chains...

However, one needs to take into account that all the calculations are done assuming a temperature of 0 K, and hence at room temperature these couplings will be minimal. Furthermore, in collaboration with Beljonne and co-workers, transition densities were calculated [25] for excitation transfer between two per-yleneimide chromophores coupled by a fluorene trimer (separation 3.4 nm) and found to be in line with the Forster approximations. 

Experience on the calculation of the fifth CH overtone has shown that a very accurate description of the chromophore coupling is required. Consequently, an eighth-order description of the coupling between the chromophore modes, W(qu q5), has been used in order to represent the CH chromophore accurately. This potential operator, determined by Quack and colleagues (91), very accurately reproduces the chromophore spectrum through N =6. 

In this connection, the importance of fatigue resistance should be pointed out. If form A of a chromophoric couple A/B undergoes a side reaction with a quantum yield d>side=0.001 and B converts to A without loss, 63% of the initial molecules of A will be decomposed after 1000 cycles. Thus, 0side should be less than 0.0001 if the system is expected to endure more than 10" cycles [65]. 

Photoinitiated electron collection in polyazine chromophores coupled to water reduction catalysts for solar H2 production 13CCR 1660. 

Spectral dynamics of a chromophore coupled to one or many two-level systems... 

Sturgis JN, and Robert B. The role of chromophore coupling in tuning the spectral properties of peripheral light-harvesting protein of purple bacteria. Photosynth. Res. 1996 50 5-10. 

S. A. Egorov, E. Gallicchio, and B. J. Berne,/. Chem. Phys., 107, 9312 (1997). The Simulation of Electronic Absorption Spectrum of a Chromophore Coupled to a Condensed Phase Environment Maximum Entropy Versus Singular Value Decomposition Approaches. 

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