Spin conversion viscosity dependence

M(H) from Eq. (3.561) shown in Figure 3.71(a). Following from these data, the extremal viscosity dependence of MFE at any given field [Fig. 3.71(h)] has a plausible explanation within the same unified theory but with the coherent spin conversion in the reduced (two spin states) basis [32,149]. The latter simplification was removed in the subsequent work where all four states were considered [150]. 

The only difference from the single-channel EM outlined above (Section V.A) is the substitution of k et by the sum of the spin-allowed and spin-forbidden transfer rates k et + k c, to the ground and triplet states, respectively. Like k-eh the intersystem crossing rate kKC does not depend on viscosity. Moreover, EM does not separate the two different steps of the forbidden transition spin conversion to the triplet RIP and subsequent allowed electron transfer into the triplet product [212-216]. However, as has been shown in Section XI.A, even in the case of a single channel but spin-forbidden reaction (I), one should discriminate between the spin conversion and subsequent recombination through electron transfer. The qualitative difference between the spin-allowed and... 

As has been shown, the fitting of the linear viscosity dependence of chemiluminescence is completely different if the geminate recombination is considered alone or accompanied by the bulk reaction. In the former case the faster the spin conversion, the better, while in the latter case it can be set to zero provided the rate of electron transfer through the triplet channel is high enough. A similar alternative will be presented in the next section. There the combination of geminate and bulk reaction appears more preferable, especially because the spin conversion carried out by the hyperfine interaction is usually weak. 

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