Pople-Walmsley defect

Figure 4 Structure of (a) a Pople-Walmsley and (b) a Su-Schrieffer-Heeger bond-alternation defect (soliton) in PA the changes in bond orders (a, dotted and b, full line) are shown underneath. The energy of PA as a function of bond order is shown in (c) the spin-charge (s-q) relations for different occupancy of the soliton energy-level are shown in (d)...

Fig. 36.13. Top Pople and Walmsley misfit, bottom Su, Schrieffer and Heeger soliton defect.

Pople and Walmsley considered that the energy required to form a pair of defects in the linear polyene molecule [H(CH=CH) H] is relatively low and should lead to a significant thermal population. They estimated the number of unpaired spins at about one per 70 carbon atoms at room temperature [26]. The observed values were much lower, 3.0 x 10 and 2.2 x 10 spin/g, for 97% trans- and 93% c7.v-polyacetylene, respectively, or one spin per 3000 and one per 10,000 carbon atoms, re-... 

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