Near-Isotropic Molecules

1958) show in this way a slight apparent anisotropy connected phenomena are that these supposedly isotropic substances give measurable depolarization factors for the Rayleigh light scattered by them (Caban-nes, 1929 Bhagavantam, 1940 Stuart, 1952). Clearly, therefore, equations (23)—(27) have some minor inadequacies. 

Qualitative explanations advanced prior to 1952 were reviewed by Stuart in his book of that date. Le F vre et al. (1956) attempted an a priori quantitative treatment of anomalous anisotropy in centro-symmetric non-polar structures along lines used previously for atomic polarizations (Le Fevre and Rao, 1954, 1955). The expression reached for the mK of a CX4 molecule involved link moments pcx, c—x and i x, stretching and bending force constants, effective charges on atoms, and the rates of change of b% x and with elongation or contraction 

Apparent Molar Kerr Constants of Some Quasi-spherical Molecules 

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The values for Cl2 are bx = 6.60, b2 = 3.62, both x 10 24 cm3. When these values are substituted in Eq. 43 together with R = 1.99 X 10 8 cm, one obtains ax == 1.79 and a2 = 2.36, both X 10 24 cm3. Thus, although the polarizability of the chlorine molecule is almost twice as great parallel than perpendicular to the axis, the atom is nearly isotropic with slightly greater polarizability perpendicular to the axis. 

Interest in the structures and properties of fullerenes has received new impetus from the recent discovery that the molecules Cm and C70 can be prepared in large quantities by comparatively simple procedures. The ready availability of solid samples of Cm and C70 now permits their characterization by a variety of physical methods. In this paper, we report the results of solid-state C nuclear magnetic resonance (NMR) measurements on powder samples of Cm and of a mixture of Cm and C70. Our NMR results indicate that Cm rotates rapidly and nearly isotropically in the solid state at 296 K and that C70 also rotates at 296 K, although somewhat anisotropically. The rotation of Cm molecules becomes slow on the time scale of our measurements at about 100 K. 

Rotation of the water molecules. Since this rotational motion is probably nearly isotropic, the incoherent scattering law is given to a good approximation by the Sears formula [19]. 

The reduced correlation times of liquid PH3 and PD3 are almost identical. This shows that the molecular reorientation is dominated by inertial effects. These can be expected to be nearly isotropic, because PH3 and PD3 are approximately spherical top molecules [5,11], Also, a comparison of the x values from relaxation measurements in [12] (reflecting both spinning and tumbling motions) with those from Raman spectra (indicative solely of the tumbling motion) show that the rates of spinning and tumbling motions for both PH3 and PD3 are nearly equal [8],... 

In addition, this compound shows a nearly isotropic electrical and optical conductivity in the be plane,and a very distinctive structure. The latter consists in a bidimensional sheet of dimerized (BEDT-TTF) molecules where one dimer is nearly orthogonal to the neighbouring ones, and they do not form the usual face-to-face piling along the stacking axis. The Cu(NCS)2 counter anion builds a shee where the copper coordinates with a sulfur atom and two nitrogen one to form a coordination polymer... 

Biaxially oriented PP (BOPP) film is a highly transparent, stiff film. The film can be produced using a blown film or tenter process. Stretching in both the machine direction and transverse direction is carried out at a temperature below the melting point of the polymer and results in the partial orientation of molecules in the direction of stretch. The film produced by the blown process is nearly isotropic in both the directions while the film produced by the tenter process tends to be more highly oriented in the direction of machine. The cost of the tenter process equipment is much higher in comparison to blown film equipment. 

Whereas orientations of the water molecules at interfaces with different organic liquids appear to be similar, orientational ordering of organic molecules vary. Small molecules, such as CCI4 and DCE, are oriented nearly isotropically whereas the... 

Typical shapes of the orientation distribution function are shown in figure C2.2.10. In a liquid crystal phase, the more highly oriented the phase, the moreyp tends to be sharjDly peaked near p=0. However, in the isotropic phase, a molecule has an equal probability of taking on any orientation and then/P is constant. 

Lateral density fluctuations are mostly confined to the adsorbed water layer. The lateral density distributions are conveniently characterized by scatter plots of oxygen coordinates in the surface plane. Fig. 6 shows such scatter plots of water molecules in the first (left) and second layer (right) near the Hg(l 11) surface. Here, a dot is plotted at the oxygen atom position at intervals of 0.1 ps. In the first layer, the oxygen distribution clearly shows the structure of the substrate lattice. In the second layer, the distribution is almost isotropic. In the first layer, the oxygen motion is predominantly oscillatory rather than diffusive. The self-diffusion coefficient in the adsorbate layer is strongly reduced compared to the second or third layer [127]. The data in Fig. 6 are qualitatively similar to those obtained in the group of Berkowitz and coworkers [62,128-130]. These authors compared the structure near Pt(lOO) and Pt(lll) in detail and also noted that the motion of water in the first layer is oscillatory about equilibrium positions and thus characteristic of a solid phase, while the motion in the second layer has more... 

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