By Kev M. Salikhov
In the final twenty years it used to be validated that, as well as plenty and fees, magnetic moments of nuclei may be able to impact remarkably chemical reactions. This booklet provides the actual history (both theoretical and experimental) of the magnetic isotope results in radical reactions in strategies. specified consciousness has been paid to the quantitative interpretation of the on hand experimental facts. This publication should be precious for physicists, chemists and biologists using the isotope influence of their investigations in addition to for these keen on isotope separation and isotope enrichment initiatives. also, the magnetic isotope influence seems to be very important in geochemistry and cosmochemistry. The ebook could be prompt for postgraduates and senior undergraduate students.
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Extra info for Magnetic Isotope Effect in Radical Reactions: An Introduction
D·d ~ gfJ 3Yn = 1. 33) , where Yn is measured in units rad/(T' s). For example, Eq. d ~ 5 . 10 8 rad/s for protons and ca. 8· 10 7 rad/s for deuterons. In contrast to the isotropic hf coupling the dipole-dipole interaction strongly varies with molecular motion: molecular motion causes random time modulation of the dipole-dipole interaction given by Eq. 32). , ). For example, the electron paramagnetic resonance spectra in liquids show splitting into several components due to isotropic hf coupling: the EPR spectra exhibit hf structure.
Dependence of the MIE parameter Ta on the recombination rate constant Ks (a) and on the isotropic hf coupling constant A (b) according to Eq. 8), calculated within the continuous diffusion model. 03 nm. , ro = b. D = 10- 6 cm2/s, the isotropic hf coupling constant is equal to 1 mT for a, and Ks = = 1000 ns- 1 for b, and 1= 112. 1-1 mT. The numerical results presented in Fig. 2 show that the largest possible contribution of an hfi to the RP recombination can be expected to appear only at very high hf coupling constants.
1 Radical pairs with one magnetic nucleus 57 One could expect that, with increasing a1:D and Ks'Z;" the RP recombination probability would tend towards one, Tp(S) -+ 1. In this case the isotope enrichment parameter T a might be very large. However, this does not happen. As was discussed in the previous chapter, the total spin of electrons and nuclei in zero magnetic field has to be conserved when isotropic hf coupling alone is responsible for S-T conversion. As a result, not all triplet RPs can be converted to the singlet state.