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181.
Milikisyants S Groenen EJ Huber M 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,192(2):275-279
By pulsed double electron-electron resonance (DEER), distances between spin labels in disordered systems up to 8 nm can be measured. In addition, the relative orientation of the interacting radicals can be determined, provided that the bandwidth of the pulses is sufficiently small. On the other hand, the bandwidth has to exceed the dipolar interaction considerably, because otherwise the DEER modulations become distorted and the modulation depth decreases, making distance determination impossible. Therefore, small bandwidths, i.e. long pulses, place a lower limit on the distance that can be determined. Two new pulse sequences, observer-selective DEER (os-DEER) and dead-time free os-DEER, are introduced that make it possible to use long observer pulses with bandwidths that are smaller than the dipolar interaction. The new pulse sequences do not suffer from the distortions caused by the limited bandwidth of the observer pulses, as demonstrated by measurements on a nitroxide biradical. With observer pulses of 140 ns, i.e., significantly longer than the 32 ns used in the conventional DEER sequence, a dipolar interaction of 7.8 MHz has been measured. 相似文献
182.
Yu-Hong Huang 《Applied Surface Science》2009,255(7):4347-4350
A small sandwiched transition region between the Au catalysis droplet and silicon nanowires (SiNWs) is proposed to investigate the diameter-dependent orientation of SiNWs grown by the vapor-liquid-solid (VLS) mechanism. Atomic-scale calculation shows that for a given transition region width, there is always a critical diameter. Below the critical value, surface energy dominates and the 〈1 1 0〉 orientation is preferred, whereas at larger diameters, the interphase energy dominates and SiNWs grow along the 〈1 1 1〉 direction. The variability of the critical diameter is also included in our model by adjusting the transition region width. The theoretical results are in agreement with those from experiments. 相似文献
183.
红外透过、反射吸收光谱研究手性液晶(M1)LB膜的结构与取向 总被引:2,自引:1,他引:2
利用FTIR光谱研究了一种手性液晶化合物(M1)LB膜的结构与取向,该化合物可以形成稳定的单层与多层膜。手性分子中,芳香环平面向于垂直基片表面,分子中的烷基链部分则与基底表面法线方向成一定的角度。 相似文献
184.
The [(Pb0.90La0.10)Ti0.975O3/PbTiO3]n (PLT/PT)n (n = 1-6) multilayer thin films were deposited on the PbOx(1 0 0)/Pt/Ti/SiO2/Si substrates by RF magnetron sputtering method. The layer thickness of PbTiO3 in one periodicity kept unchanged, and the layer thickness of (Pb0.90La0.10)Ti0.975O3 is varied. The electrical properties of the (PLT/PT)n multilayer thin films were investigated as a function of the periodicity (n) and the orientation. The studied results show that the PbOx buffer layer results in the (PLT/PT)n films’ (1 0 0) orientation, and the (1 0 0)-oriented (PLT/PT)n multilayer thin films with n = 2 exhibit better pyroelectric properties and ferroelectric behavior than those of (PLT/PT)n films with other periodicities and orientations. The underlying physical mechanism for the enhanced electrical properties of (PLT/PT)n multilayer thin films was carefully discussed in terms of the periodicities and orientations. 相似文献
185.
Hai Guo Xudong Yang Teng Xiao Weiping Zhang Liren Lou Jacques Mugnier 《Applied Surface Science》2004,230(1-4):215-221
Pure and rare earth doped gadolinium oxide (Gd2O3) waveguide films were prepared by a simple sol–gel process and dip-coating method. Gd2O3 was successfully synthesized by hydrolysis of gadolinium acetate. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study the thermal chemistry properties of dried gel. Structure of Gd2O3 films annealed at different temperature ranging from 400 to 750 °C were investigated by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that Gd2O3 starts crystallizing at about 400 °C and the crystallite size increases with annealing temperature. Oriented growth of (4 0 0) face of Gd2O3 has been observed when the films were deposited on (1 0 0) Si substrate and annealed at 750 °C. The laser beam (λ=632.8 nm) was coupled into the film by a prism coupler and propagation loss of the film measured by scattering-detection method is about 2 dB/cm. Luminescence properties of europium ions doped films were measured and are discussed. 相似文献
186.
Ping Yang Manfred Wendisch George Kattawar Yongxiang Hu 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(12):2035-2039
This note reports on the effects of the polarization state of an incident quasi-monochromatic parallel beam of radiation and the orientation of a hexagonal ice particle with respect to the incident direction on the extinction process. When the incident beam is aligned with the six-fold rotational symmetry axis, the extinction is independent of the polarization state of the incident light. For other orientations, the extinction cross-section for linearly polarized light can be either larger or smaller than its counterpart for an unpolarized incident beam. Therefore, the attenuation of a quasi-monochromatic radiation beam by an ice cloud depends on the polarization state of the beam if ice crystals within the cloud are not randomly oriented. Furthermore, a case study of the extinction of light by a quartz particle is also presented to illustrate the dependence of the extinction cross-section on the polarization state of the incident light. 相似文献
187.
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189.
A series of amino silicones with different amino values were synthesized and adsorbed onto surfaces of cotton fibers and cellulose substrates. The film morphology, hydrophobic properties and surface composition of the silicones are investigated and characterized by field emission scanning electron microscope (FESEM), atomic force microscope (AFM), contact angle measurement, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared (ATR-IR). The results of the experiments indicate that the amino silicone can form a hydrophobic film on both cotton fibers and cellulose substrates and reduce the surface roughness significantly. Furthermore, the roughness becomes smaller with an increase in the amino value. All these results suggest that the orientation of amino silicone molecule is with the amino functional groups of amino silicone molecule adsorbed onto the cellulose interface while the main polymer chains and the hydrophobic Si-CH3 groups extend toward the air. 相似文献
190.
Y. Okada 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(9):1719-1742
We studied numerical orientation averaging with three methods for selection of orientations: lattice-grid division, crude Monte-Carlo (CMC) method, and quasi-Monte-Carlo (QMC) method. Numerical orientation averaging with these methods are carried out with a fixed orientation version of the T-matrix method for clusters of spheres. The errors of numerical orientation averaging as a function of number of orientations are investigated by comparison with results from analytical orientation averaging of the T-matrix method.We studied four types of aggregates: a bisphere, ballistic cluster-cluster aggregates of 4 and 128 monomers (BCCA4 and BCCA128), and a ballistic particle-cluster aggregate of 128 monomers (BPCA128).We studied convergence of the scattering efficiency Qsca, absorption efficiency Qabs, asymmetry parameter g, intensity , and degree of linear polarization P=-S12/S11. For the polarization, scattering angles of maximum (Θmax) and minimum (Θmin) polarization in results of analytical orientation averaging are considered. For the intensity, in addition to Θmax and Θmin, forward scattering angle (Θ=10°) is also considered.Qsca, Qabs and g of bisphere, BCCA4, and BPCA128 can be obtained accurately with smallest number of orientations by using QMC among three methods. Errors in Qsca, Qabs and g of BCCA128 were already small for smaller number of orientations (e.g., 100) with all the three methods.P(Θmin) generally shows slow convergence requiring several thousands of orientations to have errors less than 1%. There are also cases where convergence of P(Θmin) within 1% error is not attained even for largest number of orientations studied in this paper (i.e., BCCA4 with lattice-grid, BCCA128 with lattice-grid, BCCA128 with CMC).Intensity of Θ=10°, Θmax and Θmin, and polarization of Θmax generally show convergence within 1% error for several hundreds to 1000 orientations with three methods for selection of orientation angles. Among three methods, QMC requires smallest number of orientations for intensity and polarization.We also investigated convergence of Θmax and Θmin. Convergence of Θmax and Θmin is generally attained for 100-1000 orientations.We also described the application of the method to the discrete dipole approximation. In these calculations, we considered three shape models with different number of dipoles and different dipole representations to describe BCCA4. The results show that scattering and absorption efficiencies, and asymmetry parameter can generally be obtained within 1% errors for all the three shape models. On the other hand, errors are larger for intensity (up to 10%) and polarization (up to 50-70%). 相似文献