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41.
A Brillouin investigation in CsHSeO4 has been performed over the temperature range 20–165 °C which includes two phase transitions, in particular the transition to the superionic phase near Ts = 129 °C. We observed strong discontinuities for elastic constants C11, C22 and C33 at Ts and a broadening of the Brillouin lines above Ts. The results are discussed on the basis of a linear coupling between strains and mobile protons. 相似文献
42.
A. Li Bassi C.E. Bottani B.K. Tanner A. Stella P. Tognini P. Cheyssac R. Kofman 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(1):31-38
The abrupt change of velocity in surface acoustic waves in thin films of amorphous SiOx containing nanometre scale -Sn crystals is shown to be directly associated with the size-dependent melting of the nanoparticles, confirming preliminary
experiments. High resolution thin film powder diffraction using synchrotron radiation shows that the abrupt redshift in the
Brillouin spectra satellites occurs at the same temperature as the melting of the nanoparticles, evident for the loss of the
Bragg peaks. Effective medium theory is used to explain the origin of the anomaly. A central peak in the Brillouin spectrum,
the intensity of which shows a maximum at the melting temperature, can be interpreted in terms of overdamped fluctuations
in the dielectric function. The melting temperature as a function of particle size is in agreement with theoretical predictions.
No evidence for strain could be found on the X-ray diffraction profiles; the a- and c-axis thermal expansion coefficients are the same as those in bulk tin.
Received 30 March 2000 and Received in final form 24 July 2000 相似文献
43.
Thin silica-titania films doped with CdS and PbS nanocrystals have been prepared by the sol-gel route. Their nonlinear properties have been studied using the techniques of degenerated four-wave mixing and m-lines with picosecond (ps) and nanosecond laser pulses. Depending on wavelength, doping level, and laser pulse duration, high negative nonlinearity was found for CdS-doped (n2 = -2 x 10-8 cm2 per kW) and PbS-doped films (-10-10 to -2 x 10-7 cm2 per kW). The response time of the nonlinearity was below 35 ps. Saturation of the nonlinearity was observed. Straight, monomode channel waveguides have been fabricated on these films. The influence of MIE-scattering due to the nanoparticles is investigated. 相似文献
44.
Takuya Kawazu Kousuke Torii Hiroyuki Sakaki 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):226
Landau levels have been theoretically investigated in a two-dimensional electron gas near a quantum dot (QD) layer. By a diagrammatical method, we have formulated the self-energy for the Landau level and deduced its relation to the AC conductivity σloc(ω) in the QD layer. As an example, we have examined the density of states in the case where σloc(ω) is described by AωS(S=0.8). It is found that the Landau levels are broadened due to the interaction with the localized electrons in the QDs. 相似文献
45.
电化学体系中吸附在金电极表面吡啶的紫外拉曼光谱研究 总被引:1,自引:1,他引:1
观察到波长为325nm的紫外光激发下吸附在金电极表面的吡啶的表面增强拉曼光谱(SERS)。结合其SERS谱随电位的变化关系,分析了其中的增强机制并表明随电位的负移吡啶的吸附方式发生改变。 相似文献
46.
A pulse sequence producing a second stimulated echo is suggested for the compensation of relaxation and residual dipolar interaction effects in steady gradient spin echo diffusometry. Steady field gradients of considerable strength exist in the fringe field of NMR magnets, for instance. While the absolute echo time of the second stimulated echo is kept constant throughout the experiment, the interval between the first two radiofrequency pulses is augmented leading to a modulation of the amplitude of that second stimulated echo by self-diffusion only. The unique feature of this technique is that it is of a single-scan/single-echo-signal nature. That is, no reference signals neither of the same pulse sequence nor of separate experiments are needed. The new method was tested with poly(ethylene oxide) melts and proved to provide reliable data for (time dependent) self-diffusion coefficients down to the physical limit (D approximately 10(-15)m(2)/s) when flip-flop spin diffusion starts to become effective. 相似文献
47.
Li Liu Michael I. Mishchenko W. Patrick Arnott 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(15):2656-2663
We employ the numerically exact superposition T-matrix method to perform extensive computations of scattering and absorption properties of soot aggregates with varying state of compactness and size. The fractal dimension, Df, is used to quantify the geometrical mass dispersion of the clusters. The optical properties of soot aggregates for a given fractal dimension are complex functions of the refractive index of the material m, the number of monomers NS, and the monomer radius a. It is shown that for smaller values of a, the absorption cross section tends to be relatively constant when Df<2 but increases rapidly when Df>2. However, a systematic reduction in light absorption with Df is observed for clusters with sufficiently large NS, m, and a. The scattering cross section and single-scattering albedo increase monotonically as fractals evolve from chain-like to more densely packed morphologies, which is a strong manifestation of the increasing importance of scattering interaction among spherules. Overall, the results for soot fractals differ profoundly from those calculated for the respective volume-equivalent soot spheres as well as for the respective external mixtures of soot monomers under the assumption that there are no electromagnetic interactions between the monomers. The climate-research implications of our results are discussed. 相似文献
48.
《Wave Motion》2020
Analytical solutions are reported for the scattering coefficients of a solid elastic sphere suspended in a viscous fluid for arbitrary partial wave order. Expressions are derived for incident compressional and shear wave modes, taking into account the viscosity of the surrounding fluid and resultant wave mode conversion. The long compressional wavelength limit is employed to simplify the derivation, whereas no restriction is placed on the shear wavelength in the fluid compared to the particle dimension. The analytical approximations are compared with numerical results obtained from matrix inversion of the boundary equations and agree within the validity domain of the solutions. 相似文献
49.
Summary In this paper we present a vibrational-spectroscopy technique which combines the advantages of coherent anti-Stokes Raman
spectroscopy (CARS) and linear Raman difference spectroscopy. The method which we call CARS difference spectroscopy can be
applied for the study of small frequency shifts and/or bandwidth changes in the CARS spectra of liquid mixtures and solutions.
First we develop the theory necessary for the interpretation of experimental data obtained from CARS difference measurements
of mixtures of two Raman-active liquids and present some model calculations for benzene-toluene mixtures of different concentrations.
Then the experimental arrangement used for CARS difference measurements as well as some examples of recorded spectra are described.
We show that it is possible to observe the effects of dilution on CARS spectra with high accuracy by applying the discussed
technique.
Paper presented at the “XI European CARS Workshop”, Florence, Italy, 23–25 March, 1992. 相似文献
50.
利用KrF激光泵浦高压H_2,在同轴前向的受激拉曼散射(SRS)作用下,产生受激拉曼放大,1阶Stokes光对泵浦光的转换效率为17.2%,并对影响放大过程和转换效率的若干因素作了分析。 相似文献