ECHO-INDUCED EPR-SPECTRA OF NITROXIDES - STUDY OF MOLECULAR LIBRATIONS

The shapes or echo-induced EPR spectra (i.e. field dependence or ESE signal intensity) for nitroxides In organic glasses are ln good agreement with those computed for the model where magnetic relaxation ls caused by low-amplitude stochastic orientational motion of a molecule near its equilibrium position. The echo-Induced spectra depend on a single parameter only - the product 2-tau-alpha-2-tau(c) where tau is the time interval between two echo-forming pulses, alpha-2- mean squared angle or torsional motion, tau(c) - correlation time for stochastic process of motion. This motional type seems to be common for disordered molecular media with different structures. In a crystalline state this motion does not exist. So this effect could be used for a phase state determination in complex multicomponential systems (e.g. biological) using spin labeling.