The rotational dynamics of nearly spherical and cylindrical tracers dissolved in supercooled o-terphenyl is studied via the Electron Spin Resonance spectroscopy. On decreasing the temperature, a sharp crossover is ob served from the regime where the Debye-Stokes-Einstein law (DSE) holds to a new one which is accounted for by a fractional DSE (FDSE) D-r proportional to (eta/T)(?(-xi)) with xi less than or equal to 1. D-r is the rotational diffusion constant, eta the shear viscosity and T the temperature. Tumbling and spinning of the cylindrical tracer exhibit distinct crossovers. A simple model of FDSE based on the presence of dynamic heterogeneities is presented.
Evidence of a fractional Debye-Stokes-Einstein law in supercooled o-terphenyl
ANDREOZZI, LAURA;GIORDANO, MARCO;LEPORINI, DINO
1997-01-01
Abstract
The rotational dynamics of nearly spherical and cylindrical tracers dissolved in supercooled o-terphenyl is studied via the Electron Spin Resonance spectroscopy. On decreasing the temperature, a sharp crossover is ob served from the regime where the Debye-Stokes-Einstein law (DSE) holds to a new one which is accounted for by a fractional DSE (FDSE) D-r proportional to (eta/T)(?(-xi)) with xi less than or equal to 1. D-r is the rotational diffusion constant, eta the shear viscosity and T the temperature. Tumbling and spinning of the cylindrical tracer exhibit distinct crossovers. A simple model of FDSE based on the presence of dynamic heterogeneities is presented.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
