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981.
极化率测量装置是极化3He系统的重要组成部分之一.本文介绍了一套在极化3He系统上搭建的激光探测自由感应衰减核磁共振(FID NMR)信号的实验装置,该装置有望为3He极化率的高精度实时测量提供新的途径.激光探测法的原理是法拉第旋光效应,该方法使用一束线偏振光探测极化3He磁矩绕主磁场进动的FID信号,实验结果表明相较于拾波线圈探测方法,激光探测方法的信噪比提高了106%,对3He的极化率测量更精确.该探测方法有望替代传统的拾波线圈,广泛地应用于3He极化系统的极化率测量或精密测量实验中. 相似文献
982.
Decoding the electron dynamics in high-order harmonic generation from asymmetric molecular ions in elliptically polarized laser fields 下载免费PDF全文
Cai-Ping Zhang 《中国物理 B》2022,31(4):43301-043301
The high-order harmonic generation from an asymmetric molecular ion is theoretically investigated based on the Born-Oppenheimer model with two-dimensional electron dynamics. It is shown that the harmonic intensity changes periodically in elliptically polarized laser fields. The periodical character is ellipticity-dependent. By establishing the physical image, the periodicity of the harmonic intensity can be ascribed to the contributions of the ground state and the excited state. Furthermore, the electron dynamics from different electronic states can be selected via combining the elliptically polarized laser field with a static electric field. The harmonics dominated either by ground state or excited state are emitted once in an optical cycle in the combined laser field. 相似文献
983.
基于一维金属-介质周期结构的偏振分束 总被引:3,自引:1,他引:2
分析了一维金属一介质周期结构的能带特性,根据一定频率范围内TM波(磁场方向与界面平行)在结构中的负折射以及TE波的正常折射,提出了一种偏振分束器件.利用传输矩阵法(TMM)模拟了该结构对入射高斯光束的偏振分束作用,讨论了不同入射角度下的偏振分束能力,并结合实际金属参量,分析了金属层吸收对结构特性的影响.结果表明该结构在55°附近入射时有最好的性能;在吸收作用下结构偏振分束能力有一定的减小,TM波透射比发生了较大变化,TE波效果较好;随着周期数增加,结构透射比下降,但分光能力显著提高;在工作波段上随着波长增大,金属层吸收对器件的影响减弱.该结构能实现宽波段、宽角度、较高透射比的偏振分束. 相似文献
984.
X. L. Yu J. Chen S. X. Wu Y. J. Liu S. W. Li 《Journal of Raman spectroscopy : JRS》2008,39(10):1440-1443
A rutile β‐MnO2 film was grown on MgO substrate using plasma‐assisted molecular beam epitaxy (PAMBE) monitored by reflection high‐energy electron diffraction (RHEED). Polarized Raman spectra at various temperatures were obtained to investigate the influence of the helimagnetic structure on the vibrational modes of β‐MnO2. A red shift of Eg modes indicates a gradual formation of spin angles between neighboring Mn4+ ions. The intensities of the Eg and A1g modes with y‐polarized incidence increase remarkably below the Néel temperature. A new view as vibrational mode projection (VMP) indicates the interactions between the magnetic component of incident light and the helimagnetic structure. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
985.
C. -Y. Yang G. -N. Tang 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(2):245-250
We study spin transport in
normal/ferromagnetic/normal/ferromagnetic.../normal
graphene superlattices, which can be realized by putting a series of
magnetic insulator bars on top of a graphene sheet. Owing to
magnetic proximity effect, local exchange splittings will be induced
in the graphene sheet, effectively forming a magnetic graphene
superlattice. The spin polarization of tunneling conductance and the
magneto resistance (MR) exhibit oscillatory behavior with the gate
voltage. The superlattice structure leads to an enhanced spin
polarization and MR ratio, making the magnetic graphene superlattice
become very promising in spintronics applications. 相似文献
986.
理论研究了双色线偏振激光场驱动H2+分子产生椭圆偏振谐波及阿秒脉冲的特点。计算结果表明:随着不同偏振角的引入,谐波光谱呈现不规则的椭圆率。但是,随着空间非均匀效应的引入,不仅谐波谱的椭圆率可以稳定在ɛ = 0.1和ɛ = 0.3之间,而且谐波发射的截止能量明显增强。形成4个具有较小干涉结构带宽在406 eV,299 eV,381 eV和582 eV的超长平台区。最后,通过傅里叶变换,可获得5个脉宽及椭圆率为24 as (ε = 0.1),22 as (ε = 0.3),24 as (ε = 0.3),19 as (ε = 0.3),19 as (ε = 0.3)的阿秒X射线脉冲。 相似文献
987.
From Maxwell’ s equations for electromagnetic fields, time-averaged energy flow density vector of stable monochromatic linearly
polarized light in an isotropic insulative nonmagnetic medium is deduced. By the introduction of time-averaged energy flow
density rays and the definition of new generalized refractive indexn
G1, Fermat’s principle of geometric optics is further generalized and its application conditions are discussed. The generalized
Fermat' s principle can be used to describe stable transmission of light in a medium with variable refractive index. The necessary
and sufficient conditions of a nondivergent and nonfocusing light beam are derived from this Fermat’s principle.
Project supported by the National Natural Science Foundation of China (Grant No. 69789801) and Guangdong Provincial Natural
Science Foundation of China. 相似文献
988.
989.
对于不小于波长或可与波长相比的大粒子集合性的相干散射,要求严格求解多次散射的Maxwel方程。作者利用多个粒子多次散射的严格的T矩阵公式,发展了数值模似算法,求出非均匀群聚分布的球形粒子相干极化散射在全方位上的数值结果,研究了群聚粒子相干极化散射的特征表现,并与双球粒子散射的实验结果作了很好的比较。 相似文献
990.
Nicolas Gogibus Ulrich Maschke Farida Benmouna Bernd Ewen Xavier Coqueret Mustapha Benmouna 《Journal of Polymer Science.Polymer Physics》2001,39(5):581-588
The phase diagrams of poly(dimethylsiloxane) (PDMS) and 4‐cyano‐4′‐n‐pentyl‐biphenyl (5CB) mixtures are studied for two systems of different molecular weights of the polymer. The experimental diagrams are established by polarized optical microscopy (POM), and analyzed using a combination of the Flory–Huggins theory of isotropic mixing and the Maier–Saupe theory of nematic order. The results are compared with those of polystyrene (PS) and 4‐cyano‐4′‐n‐octyl‐biphenyl (8CB) with analogous molecular weight of the polymer. This investigation could be useful for the choice of systems in electro‐optical devices. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 581–588, 2001 相似文献