title: Dynamics at the liquid-vapor interface of a supercooled organic glass former.
abstract: We investigated the dynamics near the liquid-vapor interface of the supercooled model organic glass former dibutyl phthalate by using surface-sensitive x-ray scattering techniques. Our results reveal significant enhancement of the relaxation rate over a wide length-scales range. The analysis of the dispersion relation of long-wavelength surface fluctuations yields a nonzero value of the share modulus near the free surface. At the molecular level, the dynamics in the near surface region (10-15 nm) is inhomogeneous. The mobility is decreasing with increasing distance from the free surface. Below the bulk glass transition, two distinct relaxation times were observed differing by 1 order of magnitude. The observed fast relaxation proves the existence of a high mobility liquidlike surface layer of 10 nm thickness on top of a frozen in bulk system.
authors.affiliation: Deutsches Elektronen Synchrotron (HASYLAB at DESY), Notkestrasse 85, 22607 Hamburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Sikorski
authors.forename: C
authors.initials: C
authors.lastname: Gutt
authors.forename: Y
authors.initials: Y
authors.lastname: Chushkin
authors.forename: M
authors.initials: M
authors.lastname: Lippmann
authors.forename: H
authors.initials: H
authors.lastname: Franz