title: Non-Gaussian nature of the alpha relaxation of glass-forming polyisoprene.
abstract: We report quasielastic neutron scattering experiments exploring the alpha relaxation in polyisoprene over an unprecedented range in momentum transfer. Corroborating and validating earlier molecular dynamics simulations, the measurements reveal a crossover from a Gaussian regime of sublinear diffusion to a strongly non-Gaussian regime at short distances. We show that a consistent interpretation in terms of a distribution of finite jumps underlying the alpha process is possible. This model leads to a time-dependent non-Gaussian parameter exhibiting all features revealed so far from various simulations.
authors.affiliation: Unidad de Física de Materiales (CSIC-UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Arbe
authors.forename: J
authors.initials: J
authors.lastname: Colmenero
authors.forename: F
authors.initials: F
authors.lastname: Alvarez
authors.forename: M
authors.initials: M
authors.lastname: Monkenbusch
authors.forename: D
authors.initials: D
authors.lastname: Richter
authors.forename: B
authors.initials: B
authors.lastname: Farago
authors.forename: B
authors.initials: B
authors.lastname: Frick