Electron spin relaxation of triarylmethyl radicals in fluid solution
| Autor: | Richard W. Quine, Colin Mailer, James R. Harbridge, Gareth R. Eaton, Howard J. Halpern, Sandra S. Eaton, George A. Rinard, Lu Yong, Eugene D. Barth |
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| Rok vydání: | 2001 |
| Předmět: |
Nuclear and High Energy Physics
Condensed matter physics Free Radicals Pulsed EPR Chemistry Biophysics Analytical chemistry Electron Spin Resonance Spectroscopy Temperature Trityl Compounds Condensed Matter Physics Biochemistry law.invention Solutions Viscosity symbols.namesake Fluid solution law symbols Relaxation (physics) Electron paramagnetic resonance Anisotropy Raman spectroscopy Hyperfine structure |
| Zdroj: | Journal of magnetic resonance (San Diego, Calif. : 1997). 152(1) |
| ISSN: | 1090-7807 |
| Popis: | Electron spin relaxation times of a Nycomed triarylmethyl radical ( sym -trityl) in water, 1:1 water:glycerol, and 1:9 water:glycerol were measured at L-band, S-band, and X-band by pulsed EPR methods. In H 2 O solution, T 1 is 17±1 μs at X-band at ambient temperature, is nearly independent of microwave frequency, and exhibits little dependence on viscosity. The temperature dependence of T 1 in 1:1 water:glycerol is characteristic of domination by a Raman process between 20 and 80 K. The increased spin–lattice relaxation rates at higher temperatures, including room temperature, are attributed to a local vibrational mode that modulates spin–orbit coupling. In H 2 O solution, T 2 is 11±1 μs at X-band, increasing to 13±1 μs at L-band. For more viscous solvent mixtures, T 2 is much shorter than T 1 and weakly frequency dependent, which indicates that incomplete motional averaging of hyperfine anisotropy makes a significant contribution to T 2 . In water and 1:1 water:glycerol solutions continuous wave EPR linewidths are not relaxation determined, but become relaxation determined in the higher viscosity 1:9 water:glycerol solutions. The Lorentzian component of the 250-MHz linewidths as a function of viscosity is in good agreement with T 2 -determined contributions to the linewidths at higher frequencies. |
| Databáze: | OpenAIRE |
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