Transition dipole coupling model

Figure 6.5. Exciton model for the coupling of dimers. When the transition dipoles are aligned (ft, W) in a card pack fashion only the transition to n is allowed thus a blue shift in the spectrum is expected.

Herein we present calculations [6] for liquid H20 that are similar in spirit but different in detail from those of Buch [71, 110] and Torii [97]. The MD simulations are of the SPC/E model [135]. Local-mode anharmonic frequencies are generated from our most recent map developed for the H0D/D20 system [98], as are our transition dipoles. The relatively small intramolecular coupling fluctuates with molecular environment, and is determined by a separate map parameterized from ab initio calculations on clusters. The form of the intermolecular couplings is transition dipole, which is tested and parameterized from additional ab initio calculations. The effects of motional narrowing are taken into account approximately with the TAA [99]. 

The Dipole-Dipole Coupling Mechanism. In this model, two absorbing groups have a single electronic transition. 

Figure 18 Models from which the excitonic coupling between pairs of peptide groups were calculated (a) The direction and location of the transition dipole of the amide I mode (118,123) from which the coupling between two peptide groups is calculated according to a dipole-dipole interaction term [Eqaution (28)] (b) The nuclear displacements, partial charges, and charge flow of the amide I normal mode obtained from a DFT calculation on deuterated N -methylacetamide (all experiments were performed in D2O) (42). With this set of transition charges, the multipole interaction is computed, avoiding the limitations of the dipole approximation.

The fact that three peroxide-to-copper charge-transfer transitions are observed in oxyhemocyanin and oxytyrosinase led us to consider the spectral effects of bridging peroxide between two Cu(II) ions. A transition-dipole vector-coupling (TDVC) model was developed that predicts that each charge-transfer state in a Cu-peroxide monomer... 

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