Spin exchange Heisenberg

Here 0, is the isospin describing the C, orbital, Iy is the orbital exchange constant, and Jq is the Heisenberg spin-exchange constant. This Hamiltonian can describe many of the magnetic properties of TDAE-C60. 

A few papers have dealt with the effects of Heisenberg electron spin exchange on low-field DNP behavior. Bates and Drozdoski s initial description of spin exchange effects on DNP was tested against data collected at 7 mT,31 and further work by Bates showed the changes in the DNP-detected ESR spectra at 5-9.5 mT as radical concentration was increased 92 Tregubenkov et al. presented the calculated effects of spin... 

The equivalent Heisenberg, antiferromagnetic, spin-exchange Hamiltonian... 

Eastman, M.P., Bruno, G.V. and Freed, J. H. (1970) Studies of Heisenberg spin exchange. II Effect of radical charge and size,/. Chem. Phys. 52,2511-2522. 

Fig. 8. Two-dimensional exchange spectroscopy (often called 2D-ELDOR) of the spin-labeled 3K-8 peptide with mixing time T = 296 nsec. Both the 2D surface and the contour map are shown. The peaks along the diagonal are related to the absorption spectrum of the spin label. The high-held M,= - line is weak because of experimental dead time artifacts. The cross-peaks, especially those between the outermost hyperfine lines, provide direct evidence of Heisenberg spin exchange. The cross-peak intensity can be used to determine the second-order rate constant for collisions between peptides.

Randolph and Carlier used EPR spectroscopy to study the Heisenberg spin exchange reaction of nitroxide free radicals in supercritical ethane (194). The... 

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