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

Wei Huang, Ranko Richert

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


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 s 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.

Original languageEnglish (US)
Article number214501
JournalJournal of Chemical Physics
Issue number21
StatePublished - Dec 7 2010

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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