Models soliton pair

In the original SSH model, the relaxation of the 1R state goes to a charged (S /S ) soliton pair. However, once electron correlation effect is taken into account, the negative and positive solitons appear to attract one another to form an exciton. Nevertheless, ex-... 

The above problems are eliminated by a model in which there are two solitons (a bipolaron) on an infinite chain. The soliton pair can jump to the next chain isoenergetically and with a reasonable activation barrier (Figure 10). The jump probability for two solitons separated by x carbon atoms, P(x), will contain the following elements ... 

We have modeled this process and computed conductivity versus C curves which are very similar to those obtained experimentally (Figure 3). For the purposes of this discussion we will only consider qualitative aspects of the results of this model. At low C, there will be few soliton pairs of sufficiently small x for transport to take place due to the F(x) term i.e., F(x) at the peak in the Qi(x) distribution will be small. As C increases, a++ will increase superlinearly since the peak in Qi(x) will shift to lower x values where F(x) is larger. At still larger C values, a++ will level off and eventually decrease due to the small value of the Q2(x) term, as there will now be few sites available for accepting the bipolaron. Thus, the net result from this model, qualitatively, is an S-shaped curve for the spinless bipolaron contribution to the conductivity. The detailed calculations we have carried out with this model(26) bear out this qualitative discussion and yield results quite similar to the experimental data shown in Figure 3. 

Falaco solitons were reported [132] as pairs of solitons that exist on the surface of a fluid (water), and are interconnected through the third spatial dimension. Our model for the photon is a pair of 3D solitons interconnected through the fourth dimension. 

Fig. 2 Polyenes and the 2 state, (a) Schematic representation of the singlet 2Ag state in a polyene, showing its equivalent description either as a triplet-triplet or as soliton-antisoliton pair. Adapted from ref. 33. (b) Polyene-type structures discussed in the text. 1 Polydiacetylene [34,35], 2 Poly(diethyldipropargylmalonate) 136], 3 Poly(3-dodecylthienyl-enevinylene) [37], 4 Polyibenzodithiophene thiophene dioxide) [38]. R-groups denote solubilizing chains, (c) Models of singlet fission in polyenes, mediated by formation of 2Ag (left) or directly from IBu (right).

Figure 22.29 schematically shows the model originally proposed [182] for the ultrafast energy relaxation processes in PDPA films. It contains two relaxation channels [183,184] ionic, by IS and covalent, by 2Ag, which is populated following an ultrafast phonon-assisted internal conversion from the photogenerated excitons. PAg at short time is thus due to transitions from 2Ag (dark) excitons. As in long-chain polyenes [185] and f-(CH)jj [186] these excitons are subject to ultrafast recombination dynamics and this explains the ultrafast decay dynamics seen in Figure 22.28a. In degenerate ground state polymers 2Ag is unstable with respect to the formation of soliton excitations and therefore undergoes fission into two neutral SS pairs, 2Ag => 2(S° -I- S°) [18,184], followed by further separation...

In our ADMR measurements we found 8N < 0, which can be explained within the distant pair model discussed in Section III.B.2. As explained in that section, the distant pair model can be used only for spin pairs generated with equal probability of parallel (P) or antiparallel (AP) spin configuration. This is certainly not the case for the photogenerated, S . As concluded above, they are thought to be produced in pairs (5-5) from the singlet manifold and hence presumably with preference of an AP spin configuration. To solve this apparent conflict, either a spin-flip mechanism must occur or a spin-spin interaction exists between the solitons within the 5-5 pair. Such a spin-flip process may happen via the native soliton defects, 5/ (spin 1/2 radicals), which exist in... 

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