Abstract
The method for treating the evolution of the density matrix developed in the accompanying paper for many-spin systems is applied here for calculating magnetic resonance signals of a spin A interacting with a bath of N identical spins B. Spins B are assumed to have much smaller gyromagnetic ratios than the spin A (e.g., the former are nuclear spins, I and the latter is an electron spin, S). The experimentally observed quadratic dependence of the spin-echo envelope decay on concentration and time is explained from considering the dipolar coupling of spin A to all the B spins in the presence of B–B dipolar interactions. It is shown that the spin-echo envelope decay in the rigid limit is due to the interaction of the A spin with the coherent many-body states of the coupled spins B via the nuclear flip-flop terms I±I∓, which becomes a dissipative mechanism in the thermodynamic limit. This represents a more rigorous analysis than simplified models based on an incoherent version of “spin diffusion,” and it leads to good quantitative agreement with experiment. Moreover, this analysis represents a unified description of both the modulation and decay of the A-spin echoes. Spin echoes and line shapes for the A–BN systems are also calculated for finite motions which randomize the B spins. Even for very slow motions (modeled as translational diffusion) an effective mechanism for spin-echo envelope decay is generated, which readily overtakes the coherent mechanism in importance. The intensity distribution for the forbidden components in the A-spin line shape resulting from multiquantum transitions of the B spins caused by the pseudosecular interaction terms SzI±, is calculated. In the rigid limit it is found to behave like a Poisson distribution.
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Dates
Type | When |
---|---|
Created | 23 years, 1 month ago (July 26, 2002, 9:26 a.m.) |
Deposited | 1 year, 6 months ago (Feb. 6, 2024, 6:44 p.m.) |
Indexed | 1 year, 6 months ago (Feb. 6, 2024, 7:30 p.m.) |
Issued | 24 years ago (Aug. 8, 2001) |
Published | 24 years ago (Aug. 8, 2001) |
Published Print | 24 years ago (Aug. 8, 2001) |
@article{Nevzorov_2001, title={A many-body analysis of the effects of the matrix protons and their diffusional motion on electron spin resonance line shapes and electron spin echoes}, volume={115}, ISSN={1089-7690}, url={http://dx.doi.org/10.1063/1.1382817}, DOI={10.1063/1.1382817}, number={6}, journal={The Journal of Chemical Physics}, publisher={AIP Publishing}, author={Nevzorov, Alexander A. and Freed, Jack H.}, year={2001}, month=aug, pages={2416–2429} }