From heterogeneous probe rotation to the hydrodynamic limit

Dielectric study of probe rotation in viscous liquids

“…By virtue of the concentration dependence, the lower frequency peak can be attributed to the probe dynamics without ambiguity. More quantitatively, 88% of the polarization of the guest is relaxed by the peak marked 'guest' in figure 2, while the 'host' peak contains the residual 12% of the probe relaxation signal [31]. The goal of analyzing the loss profiles is the separation of the dielectric spectrum into the signals originating from the guest ('g', DBE) and host ('h', 3MP) molecules.…”

“…Dielectric relaxation experiments in glass-formers 377 exchange or finite heterogeneity lifetime is made responsible for the averaging process required to explain the exponential rotation observed for the slower probes [31]. The time scale ex of rate exchange is always slower than the average structural relaxation time, but has to be faster than the probe rotation time to be responsible for exponential probe dynamics.…”

“…Master plot of the dielectric loss of a 1 wt% mixture of di-n-butylether (DBE) in 3-methylpentane (3MP) measured in the 50 Hz to 20 kHz range[31]. Loss profiles (symbols) from seven temperatures between 88.0 and 99.7 K are scaled in frequency and amplitude to match the result for T ¼ 93.8 K. The solid line represents a fit using the sum of two HN processes; the dashed lines represent the individual contributions.374W.…”

The Johari–Goldstein β-relaxation of glass-forming binary mixtures

“…If one component is polar and the other has a negligible dipole moment, using dielectric spectroscopy the dynamics of the polar one can be selectively studied. In literature, dielectric spectroscopy studies on binary mixtures with high dipolar contrast have been performed since decades [7,11,[24][25][26][27], although only recently the effects of concentration [28,29] and solute molecular size [30,42] have been systematically studied. However, very little attention was devoted to the relation between β-relaxation time and α-relaxation timescale and dispersion.…”

Translational diffusion of probe molecules under high pressure: A study by fluorescence recovery after photobleaching technique

“…37 The probe size effect has been extensively studied by different techniques such as holographic FRAP technique, 31 time resolved optical depolarization, 36 or dielectric spectroscopy of probe molecules having a large dipole moment in a non-polar host liquid. 38,39 Probe molecules of size close to the host molecules follow the dynamics of the heterogeneities, while large-size probe molecules exhibit a slowing down of the rotational motion. Diffusive largeprobe molecules would restore the S − E like diffusive behavior.…”