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1.
Independent measurements of the linewidth of the depolarized Rayleigh line in the critical mixture of nitrobenzene and n-hexane, persistently disagree with each other. We thus analyse here the limitations of the experimental methods and show that the strong critical narrowing observed by Fabelinskii et al. is probably an experimental artefact. 相似文献
2.
The width of phonon lines in the Raman spectra of ideal isotopically pure solids is determined by inelastic scattering processes. In solids that contain a mixture of different isotopes of one atomic constituent, elastic scattering due to isotopic mass disorder opens up decay channels that result in additional line broadening. We use different polytypes of SiC with an associated number of Raman active modes in order to experimentally validate the proportionality between linewidth and phonon density of states predicted by a simple elastic scattering theory. 相似文献
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Simultaneous stimulated Raman scattering at the 992 cm–1 and the 3063 cm–1 line of benzene is observed by mode-locked ruby laser pulse excitation. The double line stimulated Raman scattering is initiated by self-focusing. The influence of small-scale self-focusing, self-phase modulation, and cross-phase modulation on the double line stimulated Raman scattering is discussed. At low pump pulse intensities, before the onset of small-scale self-focusing, the steady-state Raman gain factors of both Raman lines are determined by Raman energy conversion efficiency measurements. 相似文献
5.
The probability density function p(I) is theoretically and experimentally investigated in the case of single, double, and multiple light scattering near a second-order transition (demixing of the binary mixture nitrobenzene and n-hexane). Experimentally we find no differences between the statistics of singly, doubly or multiply scattered light, and as expected from theory, p(I) shows an exponential variation. These results justify the use of either heterodyne or homodyne techniques for studying single or multiple scattering close to a critical point. We also describe a particularly simple way of determining whether homodyne or heterodyne detection occurs. 相似文献
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Ordered phases formed by surfactants in water solutions, and used in technological processes as templates for the synthesis of mesoporous materials, exhibit topological fluctuations. From the results of the Monte Carlo simulations of the lamellar phase we have established a relation between topological fluctuations and the behavior of the off-specular scattering intensity. We have defined the topological Lifshitz line. At this line the peak position in the off-specular scattering intensity moves from the zero (lamellar phase with fixed topology) to the nonzero value of the scattering wave vector (lamellar phase with fluctuating topology). 相似文献
8.
V. P. Kochanov 《Journal of Experimental and Theoretical Physics》2014,118(3):335-350
Based on a quantum-mechanical expression for the kernel of the collision integral and the dispersion intermolecular interaction potential, we have calculated the line profiles in which the collisions with scattering through large and classical small angles as well as the diffraction scattering of molecules have been simultaneously taken into account. By comparing the calculated profiles with those in the models of hard velocity-changing collisions, we show that disregarding soft collisions leads to a noticeably sharper line shape. In an effort to quantitatively process the spectra, we have parameterized the calculated profiles and obtained their algebraic approximation. 相似文献
9.
H.G. Schuster 《Physics letters. A》1973,46(3):163-164
It is shown that a measurement of the phonon line width of strong coupling superconductors by inelastic neutron scattering can be used to detect parallel parts in the Fermi surface of the metal. Recent measurements for Nb3Sn are analyzed. 相似文献
10.
It is shown that multiple scattering is of significant importance in the formation of the line width of parametric X-ray “backward”
radiation of relativistic electrons in a crystal. A theory of the line width of this radiation based on the functional integration
method is suggested. The problem of multiple scattering effects on parametric X-ray radiation is shown to be similar to the
problem of the Landau-Pomeranchuk-Migdal multiple scattering effect on the bremsstrahlung of high-energy electrons in an amorphous
medium. 相似文献
11.
Paul R. Berman 《Physics Reports》1978,43(3):101-149
A fundamental physical problem is the determination of atom-atom, atom-molecule and molecule-molecule differential and total scattering cross sections. In this work, a technique for studying atomic and molecular collisions using spectroscopic line shape analysis is discussed. Collisions occuring within an atomic or molecular sample influence the sample's absorptive or emissive properties. Consequently the line shapes associated with the linear or non-linear absorption of external fields by an atomic system reflect the collisional processes occuring in the gas. Explicit line shape expressions are derived characterizing linear or saturated absorption by two- or three-level “active” atoms which are undergoing collisions with perturber atoms. The line shapes may be broadened, shifted, narrowed, or distorted as a result of collisions which may be “phase-interrupting” or “velocity-changing” in nature. Systematic line shape studies can be used to obtain information on both the differential and total active atom-perturber scattering cross sections. 相似文献
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With its two degenerate valleys at the Fermi level, the band structure of graphene provides the opportunity to develop unconventional electronic applications. Herein, we show that electron and hole quasiparticles in graphene can be filtered according to which valley they occupy without the need to introduce confinement. The proposed valley filter is based on scattering off a recently observed line defect in graphene. Quantum transport calculations show that the line defect is semitransparent and that quasiparticles arriving at the line defect with a high angle of incidence are transmitted with a valley polarization near 100%. 相似文献
14.
Strey HH Wang J Podgornik R Rupprecht A Yu L Parsegian VA Sirota EB 《Physical review letters》2000,84(14):3105-3108
We report conclusive high resolution small angle x-ray scattering evidence that long DNA fragments form an untwisted line hexatic phase between the cholesteric and the crystalline phases. The line hexatic phase is a liquid-crystalline phase with long-range hexagonal bond-orientational order, long-range nematic order, but liquidlike, i.e., short-range, positional order. So far, it has not been seen in any other three dimensional system. By line-shape analysis of x-ray scattering data we found that positional order decreases when the line hexatic phase is compressed. We suggest that such anomalous behavior is a result of the chiral nature of DNA molecules. 相似文献
15.
L. Fu H. Schweizer H. Guo N. Liu H. Giessen 《Applied physics. B, Lasers and optics》2007,86(3):425-429
We use simple transmission line models with lumped elements of inductance and capacitance to interpret optical transmission
and reflection spectra of cut wires and cut-wire pairs in the near infrared region. The numerical values of the elements are
obtained by fitting experimental or numerical simulated reflectance and transmittance spectra. The scattering parameters and
the retrieved effective material parameters calculated from the transmission line models show good agreements with those obtained
from experiments or numerical simulations. This indicates that transmission line theory is a powerful tool for designing and
analyzing metamaterials at optical frequencies.
PACS 41.20.Jb; 78.67.-n; 78.66.Sg 相似文献
16.
S.P. AndreevYu. A. Gurvich V.A. NebogatovT.V. Pavlova 《Physica B: Condensed Matter》2011,406(22):4283-4288
A broadening of the absorption line of the classical cyclotron resonance (CR) in two- and three-dimensional semiconductors with neutral impurities of arbitrary depth is investigated. A dependence of the half-width of the classical CR line on the impurity characteristics (depth and range of the potential) is obtained in the wide range of the parameters. The broadening is studied within the Born approximation, and also at resonant and non-resonant scattering. Fundamental differences between the line broadening by neutral impurities in two- and three-dimensional semiconductors are revealed. An alternative explanation of classical experiments on electron scattering by neutral impurities (donors) is proposed. 相似文献
17.
V. P. Kochanov 《Optics and Spectroscopy》2000,89(5):684-689
A new model of line profile is proposed, which simultaneously takes into account hard and soft (in velocity) collisions leading to collisional line narrowing. It is shown that parameters of collisional narrowing and broadening obtained by processing experimental profiles on the basis of the standard model of hard collisions contain almost no contribution of diffraction scattering of molecules by buffer gas particles. The model proposed for the line profile makes possible a correct comparison of frequencies of the collision integral measured by methods of linear and nonlinear spectroscopy. 相似文献
18.
为探讨焊缝散射与板中超声导波阵列成像之间的关系,提出了将散射渡越时间矩阵作为分析工具用来开展焊缝散射对板中超声水平剪切(Shear horizontal,SH)导波直线合成孔径阵列成像影响的研究。运用散射因子和散射渡越时间矩阵描述焊缝散射,结合分析超声SH导波直线阵列信号所特有的圆锥曲线特征和合成孔径成像算法,从导波阵列信号和阵列成像机理出发,重点研究了焊缝散射因子和散射渡越时间矩阵在阵列成像中的作用。结果显示,焊缝散射易造成同一成像散射体反射声波的阵列信号形成"多峰",焊缝散射因子随之同步变大,散射渡越时间矩阵的秩随之成倍数关系增大,导致导波图像相应出现对应倍数的"条带"伪像,图像椭圆簇轨迹特征复杂化,特别是图像背景噪声增幅可达50%,图像信噪比减小幅度可达10%。成像实验验证了理论分析的有效性,表明散射渡越时间矩阵是研究焊缝散射对超声导波阵列成像影响规律的有力工具,该影响规律的揭示可为深入开展焊接板结构超声导波阵列图像处理和图像识别提供基础。 相似文献
19.
It was recently reported that a kind of graphene line defect can be fabricated in a controllable experimental way. In the present work we theoretically investigate the band structure and the electronic transport properties of a graphene superlattice formed by embedding periodically line defects in the graphene lattice. Based on the calculated results, we suggest that such a superlattice can be used as a quantum wire array which can carry much larger current than a single graphene nanoribbon. A remarkable advantage of this superlattice over other quantum wires is that the electronic transport in it is insensitive to scattering effects except that the scattering potential range is smaller than the graphene lattice constant. Moreover, we find that the anisotropy of the Dirac cone presented in this superlattice has a nontrivial influence on the universal minimal conductivity and the sub-Poissonian shot noise of graphene. 相似文献
20.
After briefly recalling the theories that have been developed for Rayleigh-Brillouin scattering in polyatomic gases in the hydrodynamic regime and which lead to various line widths for the Mountain line, experiments are described on SF6 where the central component of the scattered line is found not to be lorentzian, and to fit well with the translational hydrodynamics predictions concerning the width of the Mountain line which is dominated by diffusion. 相似文献