Cluster growth-decay process

In some theoretical treatments of the growth-decay process of clusters, growth is considered to proceed by the gain or loss of single adions, Aj. Thus, allowed reactions for the model system are... 

Contrary to expectations, on the millisecond time scale the initial drop //< in the luminescence studies of Mays and Ilgenfritz [24] did not increase significantly with the temperature-induced cluster growth but remained constant even when an infinite percolation cluster was present. Furthermore, the observed decays were always exponential (Fig. 9). Evidently, the initial drop no longer reflects the cluster size. The process responsible for it is over within 50 //s and should perhaps rather be looked upon similarly to the transient active sphere part of normal diffusion-controlled decay. The diffusion in this case is a random walk performed by the quencher on a (percolation) cluster. A stretched exponential decay would be expected for a random walk deactivation on a static cluster, as was observed close to the percolation threshold in earlier studies [23,24]. Those measurements were performed over a time window of about 50 //s, which is close to the reported value of the cluster lifetime from electrical birefringence measurements [60]. It is very likely that... 

The properties of the F band are, unfortunately, not known, making assignment of the time constants to a specific physical process difficult. In general, the growth time X, about 1 ps, appears to be independent of cluster size since the (S02) clusters produce similar values. The F band decay, x2, is altered substantially in the (S02)n clusters where the decay is slowed with increasing cluster size from about 13 ps to 65 ps for the n = 1 to 5 size range. The decay is attributed to a relaxation process that is slowed by interactions between the excited-state species and the surrounding cluster molecules. However, the exact nature of this relaxation process has not yet been determined. 

Within the frameworks of the considered mechanisms of structural relaxation it was to be expected, that clusters size decrease at testing temperature T growth should be facilitate process, proceeding according to the mechanism II and, consequently, the correlation between 1/p and clusters functionality F was expected (let us remind, that segments number per one cluster is equal to F/2 [58]). As the plot of Fig. 2.11 shows, this assumption turns out to be correct and the value 1/p extrapolates to one at [49, 59], that is, at clusters complete thermofluctuation decay [19]. 

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