Electron spin echo studies of free radicals in irradiated polymers

Abstract

h i k a w a F a c u l t y o f E n g i n e e r i n g , H o k k a i d o U n i v e r s i t y , K i t a -k u , S a p p o r o 060, J a p a n Studies of the utilization of the electron spin echo method for elucidating the nature and behavior of free radicals in 3'-irradiated polyethylene and poly(methyl methacrylate) are reviewed to demonstrate the importance and usefulness of this method generally for studying the effects of radiation on polymers. The paramagnetic relaxation was found to be largely due to the dipolar interaction between radicals and generally follow non-exponential kinetics. The dependence of the relaxations on the molecular motion and, therefore, on the site of the radicals is utilized for the relaxationresolved electron spin resonance measurement. This new technique was able to discriminate the

Relaxation Filtered Hyperfine (REFINE) Spectroscopy: A Novel Tool for Studying Overlapping Biological Electron Paramagnetic Resonance Signals Applied to Mitochondrial Complex I

“…With time-domain techniques that exploit the spin-lattice relaxation time (T 1e ) and their temperature dependency, it is also possible to distinguish between different species. With the filter effect of the stimulated echo sequence with respect to the longitudinal relaxation time, it is possible to suppress the contribution of one species (27,28). Longitudinal detection can also be used to separate EPR signals by their differences in T 1e (29).…”

Relaxation filtered hyperfine spectroscopy (REFINE)

“…To suppress the long living component it is possible to choose a shot repetition time which is shorter than the respective relaxation time T 1 . These different methods have been applied to some irradiated polymers [5], as well as to biological systems [6]. However, in terms of filter design all these methods act only as a high-or low-pass filter.…”

Electronic and Geometric Structures of Paramagnetic Diazadiene Complexes of Lithium and Sodium

“…[86][87][88] Another way employs the temperature dependence of the relaxation times in time domain EPR spectroscopy techniques. [88][89][90][91] Different paramagnetic speciess how different relaxation behaviors, especially at low temperatures. The spinlattice relaxation time constant, T 1 ,i sk nown as an intrinsic property of paramagnetic centers.…”