ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
We report on the use of ESR imaging for determining the translational diffusion constants of typical ESR spin probes in ordered and isotropic solvents. A discussion is given for a Fourier deconvolution method for determining the correct concentration profile if there is more than one hyperfine line in the spectrum of the radical as well as a spatial dependence of the spectrometer sensitivity. A simple but approximate subtraction deconvolution method is also presented. The diffusion constants for 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPONE) in the nematic and isotropic phases of the liquid crystal p-pentylbenzylidine-p-butylanaline (5,4) were determined. In the isotropic phase the diffusion coefficient is isotropic (D=2.5×10−6 cm2 s−1, at 50 °C), while in the nematic phase it was found to be mildly anisotropic. The diffusion coefficients for motion perpendicular and parallel to the director axis in the nematic phase are respectively, D⊥ =9.0×10−7 cm2 s−1, D(parallel) =6.4×10−7 cm2 s−1 at 27 °C. This is interpreted in terms of some smectic-like character in the nematic phase of 5,4. Possible improvements in the technique are also discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.450221
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