By Kev M. Salikhov
In the final 20 years it was once tested that, as well as lots and fees, magnetic moments of nuclei may be able to impact remarkably chemical reactions. This booklet offers the actual history (both theoretical and experimental) of the magnetic isotope results in radical reactions in recommendations. specified consciousness has been paid to the quantitative interpretation of the on hand experimental information. This ebook may be invaluable for physicists, chemists and biologists making use of the isotope impact of their investigations in addition to for these all in favour of isotope separation and isotope enrichment initiatives. also, the magnetic isotope impact seems to be vital in geochemistry and cosmochemistry. The publication will be instructed for postgraduates and senior undergraduate students.
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Additional info for Magnetic Isotope Effect in Radical Reactions: An Introduction
Due to the spin conservation, see Eq. 63), RPs with I = 1+ 1, 1- 1 will remain in the initial triplet (non reactive) state. T -- S transitions can only occur from (21 + 1) triplet sublevels with I = I. As a result, L = N = 21 + 1. 64) irrespective of the nuclear spin value, I ~ 1/2. 64) can be employed to obtain peT -- S)max for an RP in which one of the radicals has an arbitrary number of magnetically equivalent nuclei . For an RP with an odd number of nuclei having a half-integer spin it follows peT -> S)max= 1/3 and for an RP with an even number of nuclei having a half-integer spin, or for an RP with any (n > 1) number of nuclei having an integer spin, the total nuclear spin may be zero and hence peT -- S)max< 1/3.
2 (continued). 273 times bigger than the magnetogyric ratio of 19 7Au. The magnetic moments change with isotope substitution as well. 2). 2), etc. Concluding this brief outline, the hyperfine interaction in free radicals is characterized by coupling constants in the range of 107_10 10 rad/s. It is proportional to the magnetogyric ratio of nuclei, and therefore changes accordingly with isotope substitution. 5 Singlet-triplet transitions in radical pairs induced by the hyperfine interaction The magnetic isotope effect in radical reactions originates from the nonradiative intersystem S-T transitions in radical pairs induced by the hfi.
As a result, the RP recombines with the probability Tpg =1= O. The spin Hamiltonian, including isotropic hf coupling, the exchange interaction and Zeeman interactions of the RP's unpaired electrons is (see Eq. 59) where J(r) is the exchange integral depending on the distance r between the two radicals. Let N be the number of all possible states of the RP nuclear spins, N = IT IT (21k k n + 1)( 21n + 1) . 60) In the case considered, all sublevels of the triplet RPs are populated initially with the same probability 1/3N.