New expressions for depolarization dyadics in uniaxial dielectric-magnetic media

We present some novel expressions for the depolarization dyadics in uniaxial dielectric-magnetic media. These expressions were obtained by generalizing the Fikioris approach for extracting the singular behaviour of integrals involving the dyadic Green functions and the source current density distributions. Cubical, cylindrical and spherical geometries serve as examples for a discussion of the depolarization dyadics' dependence on geometry and anisotropy.     

Space charge studies of crosslinked polyethylene midvoltage cable insulation by thermally stimulated depolarization current,infrared/Fourier transform infrared,and scanning electron microscopy

We studied the space charge behavior in crosslinked polyethylene cable insulation with thermally stimulated depolarization current (TSDC). The role of the semiconducting layers of the cable in space charge formation was determined with several experiments carried out with two different cables. TSDC spectra were obtained through the exchange of the semiconducting layers of each cable with aluminum or silver coatings. Heteropolar current peaks at 80 and 105 °C were observed in the TSDC spectrum. As a sample was annealed at high temperatures, the creation of traps in the material was promoted, and a homopolar contribution at 98 °C developed. This homopolar mechanism was linked to the diffusion, with annealing, of ionic components from the semiconducting layers into the insulation bulk. The penetration depth of these components was studied with Fourier transform infrared in sections obtained at several depths starting at the outer surface of the cable insulation. These diffused components remained on the crystal surfaces, and they became trapping centers for free charge. Charge injection from the semiconducting electrodes and homopolar trapping of injected charges on these components took place afterwards during polarization. This process tended to saturation. Besides this mechanism, the continuous dissociation of molecules took place in the material with thermal annealing. This ionic charge generation resulted in an increase in the heteropolar contribution of the TSDC spectrum. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4164–4174, 2004     

拉曼光谱偏振特性的研究

在研究拉曼光谱偏振特性的基础上，计算出四氯化碳(CCl4)样品各简正振动模式的退偏度，设计了测量拉曼光谱退偏度的实验方案，并得到理论和实验相吻合的结果。     

Effect of Polarization Temperature on the Chain Segment Motion and Space Charge Detrapping in Polyamide 610 Film Electrets

The effect of polarization temperature on the chain segment motion and charge trapping and detrapping in polyamide 610 films has been investigated by means of thermally stimulated depolarization current (TSDC) and wide-angle X-ray diffraction (WAXD). A small part of the amorphous phase of quenched polyamide 610 changes into the crystalline state with increasing polarization temperature. There are three current peaks (named α, ρ₁, and ρ₂ peak, respectively) in the TSDC spectra. The α peak corresponds to the glass transition, the ρ ₁ peak is attributed to space charge trapped in the amorphous phase, and interphase between crystalline and amorphous phases, and the ρ ₂ peak originates from space charge trapped in the crystalline phase. By analyzing the characteristic parameters of these peaks, it was found that the increase of polarization temperature induced a decrease of the chain segment mobility and promoted the creation of structural traps in polyamide 610. The decrease of the chain segment mobility in the amorphous phase made the intensity of the α peak weak and the activation energy increased. The higher the polarization temperature, the higher the degree of crystallinity and the more charge carriers trapped in the crystalline phase. So, the increase of polarization temperature made the intensity of the ρ ₂ peak strong and increased the stability of trapped charge in the crystalline phase. The increase of polarization temperature also made the intensity of the ρ ₁ peak strong and decreased the stability of trapped charge in the amorphous phase and interphase.     

Compensated Polarization Scrambler for Raman Depolarization and Intensity Measurements on Microsamples

It has long been recognized ^1,2,3,4,5 in measuring relative intensities and depolarization ratios of Raman lines that prism and grating spectrometers have different transmittances for light polarized parallel (T_∥) and perpendicular (T_⊥) to the slit. Several methods have been used to give equal instrument response to parallel and perpendicular polarization. Stitt and Yost³ used a Nicol prism parallel to the high-transmittance direction of the spectrometer, combined with a rotatable mica half-wave plate to transmit either vector to the Nicol prism. This method has the advantage of having a higher spectrometer transmittance, but the mica plate gives exact half-wave retardation at only a single wavelength. A mica quarter-wave plate ^4,5 averages the transmittances of the spectrometer for the two polarization directions, but is also wavelength dependent. Virtually achromatic circular polarizers have been designed and constructed ^6,7, but these devices are too bulky and expensive for the clear apertures needed for fast spectrometers.     

Segment relaxation in PBT/PC and PA6/ABS blends as studied by thermally stimulated depolarization currents

The segment relaxation in two series of binary, finely dispersed poly(butylene terephthalate)/polycarbonate (PBT/PC) and polyamide-6/acrylonitrile-buta-diene-styrene (PA6/ABS) blends was studied by the method of thermally stimulated depolarization currents (TSDC) both in normal mode (global TSDC spectra) and in thermal-sampling mode (TSDC-TS). The resulting temperature dependencies and distribution functions of segment relaxation activation energy E_asr and the influence of annealing on the relaxation behavior of the mixed phases are discussed, considering the phase morphology. Common to all blends under study are lower E _asrp (the most probable value of E _asr), narrower E _asr distribution functions, and broader temperature ranges of the glass transitions in both phases of the blend compared to those of the initial components. The relationships are in good agreement with the hypothesis on the spontaneous fractionation of polymers in blends and on the breakdown of the cooperative segment mobility regions caused by the interactions between the molecular chains of different polymers. In finely dispersed small particles of the PBT-rich phase (particle diameter ≥ 0.5 μm), a degeneration of the cooperative segment (a) relaxation in a noncooperative segment (β) relaxation caused by the solution of PC molecules in PBT was detected.     

Application of Fluorescence Depolarization Method to Monitor Free Volume in Gels of Stereoregular Polystyrene

Summary: A fluorescence depolarization technique was applied to get the information on free volume among polymer chains in gel form. Four fluorescent molecules with different molecular sizes were doped throughout the gels of syndiotactic polystyrene (sPS) and isotactic polystyrene (iPS) physical gel system, and their fluorescence anisotropy values were examined in detail for a range of polymer concentrations. Consequently, the free volume among sPS chains in sPS/chloroform gels is as large as the size of molecules smaller than 1,5-dimethylnaphthalene and is consistent with that of the cavity size in the δ-empty crystalline form of sPS solids. The cause to produce δ-empty crystalline form of sPS solids and to form cocrystals between sPS and guest molecules is discussed by comparing the molar size of guest molecules with the free volume among sPS chains in gel form.     

偏振拉曼光谱在研究分子空间构象中的应用

偏振拉曼光谱是拉曼光谱中的一种,所有的激发光源和收集的散射光都有确定的偏振方向,不同方向的偏振光检测到样品的特点不同。因此,偏振拉曼光谱在表征样品时,一定要注意偏振方向的选取,以保证样品检测的准确性。文中主要以四氯化碳(CCl₄)分子为主要研究对象,通过对其退偏度的计算,推测CCl₄的振动方式。所计算的理论值,与实验值相差不大,证明了实验的准确性,同时也说明了偏振拉曼光谱的方向性。     

Numerical simulation study about spin resonant depolarization due to spin—orbit coupling

Spin polarization phenomenon in lepton circular accelerators had been known for many years. It gives new approach for physicists to study about spin feature of fundamental particles and dynamics of spin-orbit coupling, such as spin resonances. We use numerical simulation to study the feature of spin under the modulation of orbital motion in electron storage ring. The various cases of depolarization due to spin-orbit coupling through emitting photon and misalignment of magnets in the ring are discussed.     

磁光晶体Bi-YIG的磁致退偏效应

建立了磁光晶体磁致偏振特性测试系统。对Bi YIG晶体样品在大范围磁场下的退偏现象进行了测试。结果表明,达到磁饱和或接近磁饱和时,Bi YIG晶体的偏振性能最优;达到磁饱和后,随着磁场的增强,出现了磁致退偏效应。根据实验结果分析了磁致退偏效应的产生机理,并说明了磁致圆二向色性及磁致线双折射是产生退偏的原因。