Spin-Echo Experiment with NMR Spectra only Partially Narrowed by an Insufficiently Fast Motion

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Title:Spin-Echo Experiment with NMR Spectra only Partially Narrowed by an Insufficiently Fast Motion
Creators:
Jakeš, Jaromír
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 68, 7, pp. 1193-1205
Uncontrolled Keywords:Partial motional narrowing, Line shape analysis, Autocorrelation function, Spin-echo experiment, Nuclear magnetic resonance spectroscopy

Abstract

The spin-echo experiment on a spin system with only partial motional narrowing and an exponential field autocorrelation function is considered. The pattern of the intensity decrease in the echo spectra depends on the ratio τ/τ<sub>c</sub> of the time delay τ in the echo experiment to the correlation time τ<sub>c</sub> of the narrowing motion. With the large ratios (fast motion), the decrease is the same as in the case of extreme narrowing; to obtain undistorted <i>T</i><sub>2</sub> values, the ratio should be at least several units in the single-echo experiment and at least few decades in the multiple-echo experiment. With the small ratios (slow motion), the logarithmic decrease depends non-linearly on τ, and the <i>T</i><sub>2</sub> value found by the linear least-squares adjustment is much longer than that obtained from the extreme narrowing approximation. At very small ratios, the multiple echo yields about 3τ<sub>c</sub>/(ω<sub>p</sub>τ)<sup>2</sup> for <i>T</i><sub>2</sub> as compared with 1/(ω<sub>p</sub><sup>2</sup><i>r</i><sub>c</sub>) obtained from the extreme narrowing approximation; ω<sub>p</sub><sup>2</sup> is the second moment of the Gaussian line being narrowed. The expression for <i>T</i><sub>2</sub> in the multiple spin echo is similar to that previously found for <i>T</i><sub>2e</sub> in the solid multiple spin echo. The echo experiment changes the line shape, which at large τ/τ<sub>c</sub> approaches the Lorentzian one. The case of a multiexponential field autocorrelation function is also briefly considered. <p>

Title:Spin-Echo Experiment with NMR Spectra only Partially Narrowed by an Insufficiently Fast Motion
Creators:
Jakeš, Jaromír
Uncontrolled Keywords:Partial motional narrowing, Line shape analysis, Autocorrelation function, Spin-echo experiment, Nuclear magnetic resonance spectroscopy
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:68
Number:7
Page Range:pp. 1193-1205
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc20031193UNSPECIFIED
ID Code:2114
Item Type:Article
Deposited On:06 Feb 2009 17:15
Last Modified:06 Feb 2009 16:15

Citation

Jakeš, Jaromír (2003) Spin-Echo Experiment with NMR Spectra only Partially Narrowed by an Insufficiently Fast Motion. Collection of Czechoslovak Chemical Communications, 68 (7). pp. 1193-1205. ISSN 0010-0765

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