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Dynamic coupling of a small rigid probe to viscous ortho-terphenyl.

Wei Huang and Ranko Richert

J Chem Phys 133(21):214501 (2010) PMID 21142302

We have measured the dielectric relaxation of 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) as a rotational probe in supercooled ortho-terphenyl (OTP). Due to the significant dipole moment of TEMPO compared with OTP, its contribution to the loss spectra can be identified already at moderate concentrations. For time scales ranging from 10 μs to 1 s, it is found that the tumbling mode of TEMPO is a true replica of the structural relaxation of OTP regarding average time constant, relaxation time dispersion, and the temperature dependence. While the present dielectric results are consistent with a decoupling of a spinning mode (about the nitroxyl dipole axis) of TEMPO from viscosity, they do not agree with the strong decoupling of the tumbling mode derived from electron spin resonance experiments.

DOI: 10.1063/1.3506405
Version: za2963e q8zaf q8zb9 q8zc9 q8zd9 q8ze1 q8zf8 q8zge
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