Widespread Paradigm of Spin Exchange
The main provisions of the widespread paradigm of spin exchange
Below you get an organized introduction to the basic principles of the widely accepted paradigm ща spin exchange in dilute paramagnetic, a fundamental concept formed on the basis of decades of theoretical and experimental research, which is now in a state of change due to the accumulated theoretical and experimental data.
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1
An equivalent exchange of spin states is realized.
2
The slow spin exchange broadens the resonant lines of the spectra and gives a shift in the resonant frequencies of the EPR spectrum.
3
Fast spin exchange “averages to zero” all interactions responsible for the spread of the resonance frequencies of the spins. This explains the effect of exchange narrowing .
4
Each resonance line in the spectrum is described by a symmetric Lorentzian function.
5
The dipole-dipole interaction of spins only widens the lines of the spectrum, but does not contribute to the transfer of spin coherence from the interaction partner: there is no “return” of coherence.
6
A powerful microwave field broadens the resonance lines. For qualitative reasons, expressions for the effective parameters T1ef and T2eff are proposed.
7
Kinetic equations for the magnetizations of the spin subensemblies with frequencies ωk take into account spectral diffusion and energy transfer induced by spin exchange during random collisions of paramagnetic particles, spin dephasing and spin energy transfer induced by dipole-dipole interaction.