| Experimental evidence by neutron scattering of a crossover from Gaussian to non-Gaussian behavior in the alpha-relaxation of polyisoprene (2003) | |||||||||||
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| PHYSICAL REVIEW Experimental evidence neutron scattering crossover from Gaussian non Gaussian behavior the relaxation polyisoprene Arbe Colmenero and Alvarez Unidad sica Materiales CSIC UPV EHU Apartado San Sebastian Spain Monkenbusch and Richter Institut fur Festkorperforschung Forschungszentrum Julich GmbH Julich Germany Farago and Frick Institut Laue Langevin Postale Grenoble Cedex France Received December published May report incoherent quasielastic neutron scattering experiments exploring the relaxation range polyisoprene over unprecedented range momentum transfer The data corroborate and validate earlier molecular dynamics simulations and reveal the existence crossover from Gaussian non Gaussian character the main chain protons self correlation function the relaxation regime The real challenge the experiment was push the neutron techniques cover range wide possible combining two neutron spin echo spectrometers and backscattering instrument have been able study the dynamics range the low regime the shape the relaxation function was found related the dispersion the relaxation times predicted the Gaussian assumption short distances large this relationship strongly violated indicating non Gaussian regime have performed detailed comparison between the experiments and simulations different temperatures and found apart from temperature shift complete agreement Combining experiments and simulations led consistent interpretation terms distribution jumps underlying the diffusive | |||||||||||
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