EPR line shifts and line shape changes due to spin exchange of nitroxide free radicals in liquids: 6. Separating line broadening due to spin exchange and dipolar interactions.

ABSTRACT: EPR spectra of perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (PDT) are studied as functions of molar concentration, c, and temperature, T, in water and 70 wt % glycerol in water. The increase of the intrinsic line width averaged over the three hyperfine lines, B(tot), varies linearly with c with zero intercept in both solvents at all temperatures; therefore dB(tot)/dc is independent of c. The spin exchange induced dispersion, from which the spin exchange frequency, omega(e), may be computed, increases linearly with B(tot), passing through the origin in water and in 70% glycerol at high temperatures; however, at low temperatures, where dipolar interactions broaden the spectra, linearity does not prevail until B(tot) > 1 G due to a contribution of dipolar interactions to the dispe

SUBMITTER: Bales BL 

PROVIDER: S-EPMC2790056 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature