Evidence of a fractional Debye-Stokes-Einstein law in supercooled o-terphenyl
Dipartimento di Fisica, Università di Pisa - Piazza Torricelli
2, I-56126 Pisa, Italy
2 INFM, UdR Pisa - Pisa, Italy
Accepted: 20 May 1997
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 observed from the regime where the Debye-Stokes-Einstein law (DSE) holds to a new one which is accounted for by a fractional DSE (FDSE) with . is the rotational diffusion constant, η 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.
PACS: 66.30.Jt – Diffusion of impurities / 64.70.Pf – Glass transitions / 76.30.-v – Electron paramagnetic resonance and relaxation
© EDP Sciences, 1997