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Electron spin relaxation of triarylmethyl radicals in fluid solution.
- Source :
-
Journal of magnetic resonance (San Diego, Calif. : 1997) [J Magn Reson] 2001 Sep; Vol. 152 (1), pp. 156-61. - Publication Year :
- 2001
-
Abstract
- 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 micros 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 micros at X-band, increasing to 13+/-1 micros 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.<br /> (Copyright 2001 Academic Press.)
Details
- Language :
- English
- ISSN :
- 1090-7807
- Volume :
- 152
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Journal of magnetic resonance (San Diego, Calif. : 1997)
- Publication Type :
- Academic Journal
- Accession number :
- 11531374
- Full Text :
- https://doi.org/10.1006/jmre.2001.2379