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The infrared reflection spectra of a-Fe,O, were measured in the energy range 30-1000 cm '; two opticalphonon modes were observed for extraordinary ray; four optical-phonon modes were observed for ordinary ray. The optical constants were calculated by Kramers-Kronig analysis, and were also analyzed by the classical-oscillator model. From thesedielectric constants, the longitudinal and transverse optical-phonon frequencies were estimated. The Born and Szigeti eA'ective charges were calculated and the ionicities among a-Fe20, , a-Cr203, and a-A1,0, were studied. It is verified also that the generalized Lyddane-Sachs-Teller equation apply very well to a-Fe,O,.

Infrared reflectivity spectra of sintered crystal CdCr2S4 have been measured in the temperature range of 15–300 K. The frequencies of transverse and longitudinal phonon modes were determined from the spectra with the Kramers–Kronig relation. The temperature dependencies of those showed anomalously large shifts near the Curie temperature. The shifts for two modes on the higher-energy side increase and those for other two modes decrease with temperature. These shifts are described well by the terms of spin-correlation function and concluded to be originated from the spin-dependent force constant. The mode dependence of shifts is explained qualitatively from the relation between the linkage of super-exchange interaction and the direction of vibration of the ion. The effects of magnetic ordering were also observed on Szigeti effective charge, optical and static dielectric constants, and phonon damping constants. These are discussed from the viewpoint of the red shift of the absorption edge.

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The translational diffusion coefficient D was determined from dynamic light scattering measurements for oligo- and polyisobutylenes in isoamyl isovalerate (IAIV) at 25.0 °C (ϑ) and in n-heptane at 25.0 °C in the range of weight-average molecular weight M w from 1.01 × 103 to 1.76 × 106. The values of the unperturbed and perturbed hydrodynamic radii R H,ϑ and R H defined from D in IAIV and in n-heptane, respectively, were found to agree with each other in the oligomer region, indicating that the values of R H,ϑ may be adopted as those of the unperturbed hydrodynamic radius R H,0 in n-heptane at 25.0 °C. The values of the hydrodynamic-radius expansion factor αH in n-heptane at 25.0 °C are then obtained as the ratio R H/R H,ϑ from those values thus determined. The data for R H,ϑ are analyzed as usual by the use of the corresponding (unperturbed) helical wormlike (HW) chain theory. The results for αH as a function of the scaled excluded-volume parameter z̃ defined in the Yamakawa−Stockmayer−Shimada theory for the HW chain with excluded volume are consistent with the previous results for atactic polystyrene and poly(dimethylsiloxane). The implication is that the quasi-two-parameter scheme may be valid for αH as well as for the gyration-radius and viscosity-radius expansion factors α S and αη irrespective of the differences in chain stiffness, local conformation, and solvent condition. It is again found that the Barrett equation overestimates αH. This disagreement between theory and experiment may be qualitatively explained by the Yamakawa−Yoshizaki theory, which takes account of the possible effect of fluctuating hydrodynamic interaction on αH. It is also again found that αH coincides with αη within experimental error over the whole range of M w studied.

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