掺杂对随机取向团簇粒子辐射特性的影响

利用Bruggeman有效介质理论得到了占有不同体积份额杂质的团簇粒子的等效复折射率.采用离散偶极子近似方法对包含有不同化学成分的随机取向团簇粒子的散射相函数、消光、吸收、散射效率因子、单次散射反照率以及不对称因子等辐射特性参量进行了数值计算,深入探讨了掺杂量对随机取向团簇粒子辐射特性的影响.研究表明,掺杂对随机取向团...     

Depinning dynamics of driven colloids with random pinning： a numerical study

Using Langevin simulations, we have investigated numerically the depinning dynamics of driven two-dimensional colloids subject to the randomly distributed point-like pinning centres. With increasing strength of pinning, we find a crossover from elastic to plastic depinnings, accompanied by an order to disorder transition of state and a substantial increase in the depinning force. In the elastic regime, no peaks are found in the differential curves of the velocity－force dependence (VFD) and the transverse motion is almost none. In addition, the scaling relationship between velocity and force is found to be valid above depinning. However, when one enters the plastic regime, a peak appears in the differential curves of VFD and transverse diffusion occurs above depinning. Furthermore, history dependence is found in the plastic regime.     

Ab Initio Comparative Study of Zincblende and Wurtzite ZnO

By employing the first-principles pseudopotential plane-wave method, the physical properties of zincblende ZnO are investigated in comparison with those of the common wurtzite structure. Zincblende ZnO is predicted to be a direct gap semiconductor. Compared to the wurtzite structure, the zincblende ZnO is characterized by smaller bandgap and pressure coefficient, larger electron effective mass, increasing static dielectric constants and more covalent bonding. Furthermore, the optical properties including dielectric function and energy loss function of zincblende ZnO were obtained and analysed with some features. These aspects reveal promising applications of zincblende ZnO in optoelectronic devices.     

介绍一种测激光波长的方法

介绍一种测激光波长的方法冯法军（承德石油高等技术专科学校０６７０００）在《激光演示实验》（Ｔ．Ｋａｌｌａｒｄ著，松竹丰译，人民教育出版社，１９８０．）中第１５７页为“用一个刻线板测量光的波长”．该文给出的公式及图形都有缺陷，实验误差较大．本文予以补充...     

Ab initio path-integral molecular dynamics and the quantum nature of hydrogen bonds

The hydrogen bond(HB) is an important type of intermolecular interaction, which is generally weak, ubiquitous,and essential to life on earth. The small mass of hydrogen means that many properties of HBs are quantum mechanical in nature. In recent years, because of the development of computer simulation methods and computational power, the influence of nuclear quantum effects(NQEs) on the structural and energetic properties of some hydrogen bonded systems has been intensively studied. Here, we present a review of these studies by focussing on the explanation of the principles underlying the simulation methods, i.e., the ab initio path-integral molecular dynamics. Its extension in combination with the thermodynamic integration method for the calculation of free energies will also be introduced. We use two examples to show how this influence of NQEs in realistic systems is simulated in practice.     

Dynamics of a three-level V-type atom driven by a cavity photon and microwave field

We discuss the dynamics of a three-level V-type atom driven simultaneously by a cavity photon and microwave field by examining the atomic population evolution. Owing to the coupling effect of the cavity photon, periodical oscillation of the population between the two upper states and the ground state takes place, which is the well-known vacuum Rabi oscillation. Meanwhile, the population exchange between the upmost level and the middle level can occur due to the driving action of the external microwave field. The general dynamic behavior is the superposition of a fast and a slow periodical oscillation under the cooperative and competitive effect of the cavity photon and the microwave field. Numerical results demonstrate that the time evolution of the population is strongly dependent on the atom–cavity coupling coefficient g and Rabi frequency ?_e that reflects the intensity of the external microwave field. By modulating the two parameters g and ?_e, a large number of population transfer behaviors can be achieved.     

基于激光拉曼光谱的水面油膜厚度测量方法研究

为了实现水体表面油膜厚度的快速非接触检测,基于激光拉曼光谱检测技术,搭建了水体表面油膜厚度拉曼光谱检测系统。以532 nm激光作为激发光源,以常见的柴油和汽油为例研究了不同油品的拉曼光谱特性,研究结果表明,油膜拉曼光谱响应特性与油品密切相关,相同油膜厚度情况下不同油品的拉曼光谱曲线有明显的差异,97#汽油在1 651 cm-1光谱强度要高于90#汽油。随着油膜厚度的增加,柴油316和1 451 cm-1光谱强度和汽油1 651 cm-1拉曼位移光谱强度增加,油拉曼光谱信号变强;根据油水界面拉曼光谱特征,设计了油膜厚度计算因子,实验证明随着油膜厚度增加,油膜厚度计算因子r_film呈下降趋势。可以将油膜厚度计算因子作为水体表面油膜厚度测量的一种依据。     

Quantum Anomalous Hall Multilayers Grown by Molecular Beam Epitaxy

Quantum anomalous Hall(QAH) effect is a quantum Hall effect that occurs without the need of external magnetic field. A system composed of multiple parallel QAH layers is an effective high Chern number QAH insulator and the key to the applications of the dissipationless chiral edge channels in low energy consumption electronics. Such a QAH multilayer can also be engineered into other exotic topological phases such as a magnetic Weyl semimetal with only one pair of Weyl points. This work reports the first experimental realization of QAH multilayers in the superlattices composed of magnetically doped(Bi,Sb)_2Te_3 topological insulator and Cd Se normal insulator layers grown by molecular beam epitaxy. The obtained multilayer samples show quantized Hall resistance h/N_e~2, where h is Planck's constant, e is the elementary charge and N is the number of the magnetic topological insulator layers, resembling a high Chern number QAH insulator. The QAH multilayers provide an excellent platform to study various topological states of matter.     

一种新的基于频域有限差分方法的小周期有机太阳能电池的光电特性

由MoO₃/Ag/MoO₃ （MAM）组成的多层膜结构非常有希望替代ITO作为有机太阳能电池中的透明阳极.然而,基于MAM结构的有机太阳能电池光吸收能力较弱.为此,引入了一种小周期短节距金属光栅,利用表面等离子激元增强活性层的光吸收.借助于频域有限差分方法求解麦克斯韦方程和半导体方程,探讨了有机太阳能电池结构的光学和电学性质.分析结果表明：与平面结构相比,活性层中的光吸收大大提高;同时,当凹槽宽度为4 nm,能量转换效率提高了49%.相关结果有助于更好地开发和利用无ITO层的有机太阳能电池.     

不同结构六边形斑图演化过程光谱特性

采用发射光谱法,研究了水电极介质阻挡放电中具有相同对称性的3种不同结构的六边形斑图演化过程的光谱特性。实验结果表明,随着外加电压的增加,放电首先形成六边形点阵斑图,然后是空心六边形斑图,最后是蜂窝六边形斑图。利用氩原子696.5 nm(2P_2→1S_5)谱线的展宽、氩原子763.2 nm(2P_6→1S_5)与772.1 nm(2P_2→1S_3)两条谱线强度比法和氮分子第二正带系(C~3Π_u→B~3Π_g)的发射谱线,研究上述3种斑图的电子密度、电子激发温度及分子振动温度。结果发现,随着外加电压的升高,六边形点阵斑图、空心六边形斑图和蜂窝六边形斑图的电子密度逐渐减小,而电子激发温度和分子振动温度逐渐增加。等离子体状态的改变直接影响着斑图的自组织。