Contributions of Exchange and Dipole–Dipole Interactions to the Shape of EPR Spectra of Free Radicals in Diluted Solutions

Salikhov, K. M.

doi:10.1007/s00723-010-0128-x

Cited by 58 publications

(119 citation statements)

References 7 publications

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“…The motion of the transverse components of the subensemble magnetization vectors

M_{1}^{⊥}, M_{0}^{⊥}

and

M_{- 1}^{⊥}

is described by the modified Bloch equations 3,4,11,12 …”

Section: Introductionmentioning

confidence: 99%

“…The spectral densities depend on the kinematics of the molecular motion. If we assume that the molecular diffusion is described by the so-called permanent diffusion model (PDM), the spectral densities can then be calculated in terms of the translational diffusion time, τ D , as described in Section 3 of ref 4 . As can be noted from eq 4, the contribution from DD to the spin coherence transfer is opposite to that from HSE, negative for DD and positive for HSE.…”

Section: Introductionmentioning

confidence: 99%

“…4 and the X-band frequency ω = 6 × 10 10 rad/s. The first-derivative EPR spectra, dS ( ω )/ dω , as a function of the rate of DD in the absence of HSE and vice versa are presented in the Supporting Information.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Electron Paramagnetic Resonance Line Shifts and Line Shape Changes Due to Heisenberg Spin Exchange and Dipole–Dipole Interactions of Nitroxide Free Radicals in Liquids 8. Further Experimental and Theoretical Efforts to Separate the Effects of the Two Interactions

Bales

Perić

2012

J. Phys. Chem. A

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The work in Part 6 of this series (J. Phys. Chem. A 2009, 113, 4930), addressing the task of separating the effects of Heisenberg spin exchange (HSE) and dipole-dipole (DD) interactions on EPR spectra of nitroxide spin probes in solution, is extended experimentally and theoretically. Comprehensive measurements of perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (pDT) in squalane, a viscous alkane, paying special attention to lower temperatures and lower concentrations were carried out in an attempt to focus on DD, the lesser understood of the two interactions. Theoretically, the analysis has been extended to include the recent comprehensive treatment by Salikhov (Appl. Magn. Reson. 2010, 38, 237). In dilute solutions, both interactions (1) introduce a dispersion component, (2) broaden the lines, and (3) shift the lines. DD introduces a dispersion component proportional to the concentration and of opposite sign to that of HSE. Equations relating the EPR spectral parameters to the rate constants due HSE and DD have been derived. By employing non-linear least-squares fitting of theoretical spectra to a simple analytical function and the proposed equations, the contributions of the two interactions to items (1)–(3) may be quantified and compared with the same parameters obtained by fitting experimental spectra. This comparison supports the theory in its broad predictions, however, at low temperatures, the DD contribution to the experimental dispersion amplitude does not increase linearly with concentration. We are unable to deduce if this discrepancy is due to inadequate analysis of the experimental data or an incomplete theory. A key new aspect of the more comprehensive theory is that there is enough information in the experimental spectra to find items (1)–(3) due to both interactions; however, in principle, appeal must be made to a model of molecular diffusion to separate the two. The permanent diffusion model is used to illustrate the separation in this work. In practice, because the effects of DD are dominated by HSE, negligible error is incurred by using the model-independent extreme DD limit of the spectral density functions which means that DD and HSE may be separated without appealing to a particular model.

show abstract

“…The motion of the transverse components of the subensemble magnetization vectors

M_{1}^{⊥}, M_{0}^{⊥}

and

M_{- 1}^{⊥}

is described by the modified Bloch equations 3,4,11,12 …”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electron Paramagnetic Resonance Line Shifts and Line Shape Changes Due to Heisenberg Spin Exchange and Dipole–Dipole Interactions of Nitroxide Free Radicals in Liquids 8. Further Experimental and Theoretical Efforts to Separate the Effects of the Two Interactions

Bales

Perić

2012

J. Phys. Chem. A

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show abstract

“…Spin exchange and its effect on the acquired ESR spectra is well understood, experimentally as well as theoretically [108][109][110][111][112][113][114][115]. A large amount work has been done using nitroxide radicals, e.g.…”

Section: Spin Exchange Reactionsmentioning

confidence: 99%

ESR Spectroscopy of Nitroxides: Kinetics and Dynamics of Exchange Reactins

Grampp¹,

Rasmussen²

2012

Nitroxides - Theory, Experiment and Applications

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“…Very important contribution concerning correct determination of different impacts (dipole-dipole interaction, spin exchange coupling, electron spin relaxation, etc.) to the line broadening of EPR spectra was recently done by Salikhov, 2010. …”

Section: Dipolar Interaction Measured By Eprmentioning

confidence: 99%

Forty Years of the d1/d Parameter

Кокорин¹

2012

Nitroxides - Theory, Experiment and Applications

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Contributions of Exchange and Dipole–Dipole Interactions to the Shape of EPR Spectra of Free Radicals in Diluted Solutions

Cited by 58 publications

References 7 publications

Electron Paramagnetic Resonance Line Shifts and Line Shape Changes Due to Heisenberg Spin Exchange and Dipole–Dipole Interactions of Nitroxide Free Radicals in Liquids 8. Further Experimental and Theoretical Efforts to Separate the Effects of the Two Interactions

Electron Paramagnetic Resonance Line Shifts and Line Shape Changes Due to Heisenberg Spin Exchange and Dipole–Dipole Interactions of Nitroxide Free Radicals in Liquids 8. Further Experimental and Theoretical Efforts to Separate the Effects of the Two Interactions

ESR Spectroscopy of Nitroxides: Kinetics and Dynamics of Exchange Reactins

Forty Years of the d1/d Parameter

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