Chapter 5. Studies of molecular motion in liquids and solids using low frequency dielectric relaxation and related techniques

Abstract

IntroductionThe translational and reorientational motions of whole molecules or parts of molecules may be studied by spectroscopic, relaxation, and scattering techniques which cover in total the frequency range 10-4-1013 Hz. Dependent upon molecular structure and the phase (liquid, supercooled liquid, glass, crystal, or liquid crystal) and temperature and applied pressure, molecular motions may be observed anywhere in this large frequency range. For the purposes of the present account the range may be arbitrarily divided into three parts: (i) lo1' H z < v < 1013 Hz; (ii) 10' Hz< Y < lo1' Hz; (iii) Hz< Y < 10' Hz. For range (i) the fast motions of molecules are observed e.g. for small molecules in the liquid state or rotator-phase crystalline state. Such motions may be studied using near i.r. and Raman vibrationrotation spectroscopy,'*2 far i.r. ~pectroscopy,~ inelastic light-scattering spectros-copy4 (polarized and depolarized Rayleigh line-broadening) and neutron scattering ~pectroscopy,~ microwave dielectric relaxation techniques,6 and pico-second Kerreffect relaxation technique^.^ A recent text which gives the results of extensive studies of mainly non-viscous liquids is that by Lascombe.' The theoretical approach to molecular motion involves time-correlation functions, and advanced4.'-l2 and more elementary review^'^-'^ of these quantities are available

Anomalous Self-Organization in Active Piles

“…SEDs have also been observed in turbulence and earthquakes. Therefore, the Fourier transformation of SEDs is a widely used tool to describe various phenomena across multiple disciplines [60][61][62][63][64][65][66][67]. SEDs have been the focus of researchers and remain one of the oldest unresolved problems in the field (see [68] for a good review).…”

Frequency dependent study of the correlation functions in EPR spectroscopy—The Cole–Davidson approach. II. 2,N-(4-n-Butyl benzilidene) 4-amino 2,2,6,6-tetramethyl piperidine 1-oxide in toluene

“…The relaxation behaviour of a wide variety of liquids [16][17][18][19][20][21][22][23][24][25][26] is very similar irrespective of the experimental technique used and the data cannot be expressed in terms of an exponential decay with a single relaxation time [27][28][29]. In the absence of rigorous theory such data are represented in terms of empirical fitting functions.…”

Nuclear Spin Relaxation in Viscous Liquids: Relaxation Stretching of Single-Particle Probes

“…Here, single-particle (incoherent) orientational correlation refers to the autocorrelation of a molecule’s orientation at two times, whereas multiparticle (coherent) correlation refers to orientational correlation of one molecule with respect to that of another molecule. One also has to keep in mind that these spectroscopies probe different ranks l of the reorientational correlation function. , Assuming a prevalence of rotational diffusion, the time constants of the first-rank ( l = 1, probed by DS) and the second-rank ( l = 2, probed by DLS and NMR) Legendre polynomial correlation functions are expected to vary by a factor of 3, which, however, was never convincingly confirmed …”