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|Deb Narayan Nath|
|Indian Association for the Cultivation of Science, India|
|ScientificTracks Abstracts: Mod Chem appl|
|In the literature the role of viscosity on the magnetic field effect (MFE) on radical ion pair (RIP) system has been studied mainly by flash-photolysis experiment through monitoring the escape products and the inter system crossing (ISC) being taking place via Δg mechanism. In this work we have studied the effect by monitoring the singlet exciplex luminescence of pyrene-N, N, di-methylaniline (Py-DMA) system. The Noyes approach of classical Smoluchowksi equation of stochastic motion states that as the diffusivity increases, the recombination probability of geminate RIP should increase. We know that to have MFE the RIP must diffuse out to the extent of S-T degeneracy where hyperfine interaction (HFI) induced ISC can be operative and at the same time to observe the effect on singlet exciplex luminescence there should be also appreciable recombination probability. The role of diffusivity on MFE thus mainly depends on the relative distances of RIP generation and recombination. Burshtein et al has considered the spatial dispersion of free energy (ΔG) and reorganization energy (Er) and the simplified concept of exponentially decreasing CT probability W(r) (according to Marcus) changes to bell shaped curve (non-monotonous, the probability is maximum not at contact but at a certain distance) for both ionization [WI(r)] and recombination [WR(r)]. According to Burshtein model; at very high diffusivity when the system is kinetically controlled the transfer is approximated to be contact. Whereas, when ionization is controlled by diffusion (under viscous condition) the spherical reaction layer, where ions are mainly born (rg), is shown to have a greater radius than the closest approach distance. Burshtein model predicts opposite slope of MFE with diffusivity in the kinetically controlled and diffusion controlled regime.|
Deb Narayan Nath is currently working as Professor in Indian Association for the Cultivation of Science, India.
Email: [email protected]
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