Dephasing rate, electronic

An interesting result of this or a more detailed analysis [66] is that the excited-state vibrational parameters can be extracted from this type of time domain experiment even when the corresponding frequency domain observation of vibrational progressions in the Sq - Sj absorption spectrum is impossible due to inhomogeneous broadening of the electronic transition. In malachite green, the vibrational dephasing rate is about twice as rapid in Sj as in So [63]. 

We have to sttess here that there are many works devoted to the experimental measurements of y available from the literature. A commonly used electronic dephasing rate for large conjugated organic molecules in solution is y 0.1 eV... 

Figure 29. Ratio of exciton population relaxation rate (S) to the exciton pure dephasing rate (r) as a function of J/a, where J is the electronic couphng and a is the disorder, a = 150 cm for B850 of LH2. The upper curve is for = 0, and the lower curve is for Eoip = 550cm . As S/T increases, energy transfer becomes more coherent.

As shown in Section II, the rate constant of the collision-induced electronic relaxation (K/ or K /) depends on intramolecular parameters (s-/ coupling constant—and s-/ level spacing e /) as well, as on the strength of the external, collisional perturbation (expressed in (19) by the overall dephasing rate -y,/). The separation of both factors is not always self-evident. Nevertheless, for the simplicity sake we will first discuss the relation between the amount of the intramolecular s-I coupling (mixing) by assuming constant value of the intermolecular interaction. 

When, however, phonons of appropriate energy are available, transitions between the various electronic states are induced (spin-lattice relaxation). If the relaxation rate is of the same order of magnitude as the magnetic hyperfine frequency, dephasing of the original coherently forward-scattered waves occurs and a breakdown of the quantum-beat pattern is observed in the NFS spectrum. 

Equation (33) assumes that IV// is large compared to 2J (i.e., no electronic and vibrational recurrences). In addition, Eq. (33) deals only with population dynamics Interferences between different Franck-Condon factors are neglected. These interferences do influence the rate, and the interplay between electronic and vibrational dynamics can be quite complex [25], Finally, as discussed by Jean et al. [22], Eq. (33) does not separate the influence of pure dephasing (T-T) and population relaxation (Ti). These two processes (defined as the site representation [22]) can have significantly different effects on the overall rate. For example, when (T () becomes small compared to Eq. (33) substantially overestimates the rate compared to... 

The flow of energy from the ground state can also be calculated when it is assumed that the rate of electronic dephasing is small (i.e., L%Pg = 0) and/or the rate of pure vibrational dephasing is small (i.e., L%Hg = 0). These conditions apply when the rate of relaxation to equilibrium is small relative to the rate of loss of phase coherence. Under these conditions... 

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