(a) Dynamic susceptibility of o-terphenyl (normalized by relaxation strength of the α-process) as a function of frequency obtained from depolarized light scattering (tandem-Fabry-Perot interferometry and double monochromator); 90 relaxation regimes are indicated; dashed lines: “hybrid model” including α- and fast relaxation contribution, dotted lines: corresponding Cole-Davidson fit of α-peak with stretching parameter β CD = 0.64. (b) Spectra of glycerol; 73 different colors signal different relaxation regimes (cf. text); flattening of the low-frequency side of the susceptibility minimum is described by a power-law with exponent γ = 0.19 (dotted line).
The correlation function, C (2) (t), obtained from photon correlation spectroscopy (PCS) as well as from tandem-Fabry-Perot interferometry (DM/TFPI) data after Fourier transformation; dash-dotted line: fit by Kohlrausch law including excess wing contribution, solid blue line: correlation function at T = 290 K shifted to coincide with that at T = 207 K; dotted line: amplitude f of slow dynamics. 108
Minimum scaling (data from Fig. 1 ): reduced susceptibility vs. reduced frequency; below some temperature the scaling fails. (a) o-terphenyl; envelope of high-temperature data interpolated by a sum of two power-laws with exponent b = 0.65 and a = 0.33 in agreement with prediction of MCT. (b) Glycerol, colors correspond to those in Fig. 1(b) ; dotted line: interpolation with sum of two power-laws (adapted from Ref. 73 and 90 ).
(a) Dielectric loss of glycerol, 3 and propylene carbonate 84 (scaled by static susceptibility). Emergence of the excess wing contribution (arrow) is recognized; dashed line: phenomenological interpolation. 122 (b) Dynamic susceptibility (normalized by relaxation strength of α-process) of m-tricresyl phosphate as obtained by light scattering: 108 DM/TFPI spectra and PCS data transformed into the frequency domain; numbers indicate temperature; dashed lines: full interpolation of α-peak, excess wing and fast dynamics with temperature independent parameters β k, γ, and a, respectively.
Rescaled OKE data vs. reduced time t/τα of benzophenone (BZP), 77 pulse-response representation of the dielectric data of glycerol 51 and PCS data of m-tricresyl phosphate (m-TCP); 108 dashed lines indicate intermediate power-law/excess wing, dotted lines von-Schweidler law and α-process, respectively.
(a) Susceptibility spectra of the fast dynamics after subtracting α-peak and excess wing contributions from the overall susceptibility; dashed line: power-law ν0.33 of the fast dynamics; shaded area: relaxation strength 1 – f rel of the fast dynamics (adapted from Ref. 90 ). (b) 1 – f rel for α-picoline and o-terphenyl (LS), and glycerol (DS) as a function of temperature. 90,121
(a) Comparing susceptibilities of m-tricresyl phosphate as obtained from PCS (circles), from 31P NMR 95 (pentagons) and dielectric spectroscopy (diamonds); (b) susceptibility master curves of glycerol compiled from field-cycling 1H NMR (pentagons), 134 dielectric spectroscopy (circles; DS) 135 and DM/TFPI (crosses) 73,135 and PCS (solid circles); 108 dashed (blue) lines: interpolations assuming a relaxation described by a Cole-Davidson function (βCD = 0.64) together with a power-law contribution with exponent γ = 0.2; arrow indicates factor 3 between the amplitudes of the excess wing.
(a) Dielectric spectra of dimethyl phthalate (DMP) disclosing two secondary processes in addition to an α-peak. (b) Corresponding relaxation times. 141
(a) 2H NMR solid-echo spectra at different inter-pulse distances t p (see inset) for type-B glass formers; plastic crystal cyano cyclohexane (CCH), structural glasses toluene (TOL) and ethanol (ETH); spectra shown for comparable correlation times τ β = 10 μs (T < T g). (b) Corresponding spectra of the type-A glass former glycerol not displaying changes. (c) NMR spectra of cyano cyclohexane at T > T g (t p = 20 μs) revealing line-shape changes due to a loss of spatial hindrance of the β-process. 92,96,152
(a) Spin-lattice relaxation time T1 as a function of the time constant τ β of the β-process: plastic crystal cyano cyclohexane, neat structural glass formers toluene and ethanol, and binary structural glass chlorobenzene-d5/decalin (b) corresponding dielectric relaxation strength Δɛβ/Δɛ data from Refs. 49, 92, and 96 , and 152 .
(a) Susceptibility spectra of ethyl benzene obtained by applying DM/TFPI; blue curves: reflect glassy dynamics; red curves: “simple liquid” dynamics approaching the boiling point T b; green dashed line: interpolation with hybrid model assuming MCT relations for the exponents b = β and a; (b) Corresponding time domain representation of the data. 154
Reorientational correlation times of molecular liquids obtained by dielectric spectroscopy (open symbols) and light scattering (full symbols); for trinaphthylbenzene (TNB) and o-terphenyl viscosity data are included; 155,156 numbers in K: T g; straight dashed lines: high-temperature Arrhenius behavior; solid lines: full fit by Eq. (2) (adapted from Ref. 112 ).
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