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We studied by ESR the rotational motion of a paramagnetic tracer (a deuterated 15N-enriched nitroxide) in poly(vinyl acetate) (PVAc). The reorientation of the tracer occurs via jumps of about 50° with a heterogeneous distribution of correlation times. Depending on the temperature range, the average correlation time 〈τ〉 scales as the α, β, and γ relaxation times of PVAc, i.e., 〈τ〉 = C i 〈τ〉 i , i = α, β, γ. On cooling, 〈τ〉 tracks the α relaxation to about the α−β bifurcation temperature and then the β relaxation down to the glass transition. In glassy PVAc 〈τ〉/〈τ〉γ = C γ ≈ 1.

Ferroelectric domain kinetics on cleaved triglycine sulfate, quenched at different temperatures in the ferroelectric phase, is investigated in situ by scanning force microscopy in the dynamic contact mode. Thermally activated domain growth and dynamic scaling, in accordance with theoretical predictions for quenched disorder due to random-bond defects, is inferred from the temporal evolution of the spatial correlation functions and the related characteristic length scale.

Evidence of noise-induced effects in electron-paramagnetic-resonance (EPR) experiments is reported. The first observation of a stochastic resonance phenomenon in an EPR system operating in bistable conditions has been obtained. Experimental results indicate unambiguous effects on the frequency and phase of the response of the modulated bistable system in the presence of noise. Possible new progressions in the treatment of both theoretical and experimental stochastic resonance phenomenon are perceived. 05.40.+J