Current state of the spin exchange theory in dilute solutions of paramagnetic particles. New paradigm of spin exchange and its manifestations in EPR spectroscopy

Kinetic equations are presented for single-particle spin-density matrices with the Heisenberg exchange interaction in bimolecular collisions of particles and the dipole-dipole spin-spin interaction between particles taken into account. It is shown that interactions between individual paramagnetic pa...

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Bibliographic Details
Published in:Physics Uspekhi 2019-10, Vol.62 (10), p.951-975
Main Author: Salikhov, K M
Format: Article
Language:English
Subjects:
Coherence
decoherence of spin
Dilution
Dipole interactions
EPR spectrum shape
exchange and dipole-dipole interaction
exchange narrowing of spectra
Kinetic equations
Magnetism
mixed form of spectral line (absorption + dispersion)
Particle spin
Resonance lines
spin coherence transfer
Spin exchange
spin probes
spin-exchange rate constant
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Summary:Kinetic equations are presented for single-particle spin-density matrices with the Heisenberg exchange interaction in bimolecular collisions of particles and the dipole-dipole spin-spin interaction between particles taken into account. It is shown that interactions between individual paramagnetic particles, despite being rather weak compared to the exchange interaction, can result in a nonequivalent spin exchange. Spin-coherence transfer generates collective modes of quantum spin coherence motion. Collective resonance lines have a mixed form (absorption + dispersion). A new interpretation of the exchange narrowing of the spectrum when the spin-coherence transfer rate is sufficiently large is proposed. An advanced theory of paramagnetic relaxation of paramagnetic particles in dilute solutions due to dipole-dipole interaction is discussed. A modern paradigm of spin exchange is also presented.
ISSN:1063-7869
1468-4780
DOI:10.3367/UFNe.2018.08.038421