Dynamics at the liquid-vapor interface of a supercooled organic glass former |
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Authors: | Sikorski M Gutt C Chushkin Y Lippmann M Franz H |
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Affiliation: | Deutsches Elektronen Synchrotron (HASYLAB at DESY), Notkestrasse 85, 22607 Hamburg, Germany. |
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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. |
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