Role of viscosity in the magnetic field effect on pyrene–DMA exciplex emission at different permittivities

Diffusion affected magnetic field effect in exciplex fluorescence

“…Such a behavior of η e is similar to that obtained experimentally and presented in Figure 2 in Ref. 21. At the lowest D → 0, the diffusion is so slow that the fluorophore fluorescence decays before first encounter with a donor.…”

“…It should be noted that the bell-shaped curve corresponding to the largest ε = 46 is qualitatively similar to that obtained experimentally at the same (see Figure 5 in Ref. 21). The variation of k t from 0 to 10 4 Å 3 /ns (see Figure 5) leads to considerable increase of MFE, χ e , and to a shift of its maximum to the region of smaller values of D. To clarify the mechanism of this effect we note that for the parameters considered in this paper the probability of an exciplex dissociation into RIP is rather large and the probability of RIP association to produce exciplex at k t = k c = 0 varies nearly from unity to zero with variation of both D and .…”

“…Moreover, for different values of the dielectric constant the accessible ranges of the diffusion constant are not overlapped. 21 Nevertheless, the results obtained clearly demonstrate a rather strong dependence of the MFE on the diffusion constant. To get a full understanding of this dependence a theoretical analysis of the effect should be done.…”

“…21 All curves demonstrate sharp increase in the area of small diffusion constant, D, however reaching the maximum the curves go down the faster the larger ε. This results in a decrease of the maximum magnitude of η e with increasing ε.…”

“…21 Pyrene (Py) is used as the electron acceptor and N,N-dimethylaniline (DMA) as the electron donor. 21 In the experiments, the dielectric permittivity is kept inalterable, while the diffusion constant is varied. This condition strongly limits the accessible range of diffusion constant variation.…”