N2+分子离子A2∏u-X2∑+g 系(2,0)带光外差速度调制光谱

采用光外差速度调制光谱技术研究了N2+分子离子A2∏u-X2∑+g 系(2,0)带转动光谱．由于所用技术的高灵敏度特性，精确地确定了该带310条谱线的频率，其中，那些重叠谱线的频率也通过解谱精确地确定了．利用标准Hamilton量，采用非线性最小二乘方法对该带进行了分析，获得了最精确的分子常数．     

管内变密度流体的充分发展流动与换热

本文提出了圆管内变密度流体流动与换热充分发展的概念及其相关假设.在所提出的概念和假设基础上给出了摩擦阻力系数Cf与Nusselt数Nu的定义式和计算式.通过对圆管内密度随温度变化的氩气的流动与换热所进行的数值模拟,验证了在本文的计算条件范围内,圆管内变密度流体充分发展流动与换热的概念是合理的,并且CfRe=16,Nu=4.36.     

A phenomenological explanation for the buckling of surface alloys

A phenomenological model, in which the interactions between the nearest-neighbor (NN) atoms are described as bondings but not hard sphere contacts, is proposed to explain the unexpected reduced buckling in surface alloy systems. In the model, the forces acting on an adsorbate atom from its NN substrate atoms in different layers may be either repulsive or attractive, depending on whether the bond between the adsorbate atom and its NN substrate atoms is compressed or stretched. It is found that the forces on the adsorbate atom from its NN substrate atoms in the sub-surface layer play a more important role for the buckling of surface alloy than those from its NN substrate atoms in the surface layer do. The bucklings expected by the model are significantly smaller than those predicted by the simple hard sphere model and are in good agreement with the experiments when the equilibrium bond length of the NN adsorbate-substrate atom pairs is taken as the sum of the corresponding metal radii.     

Origin of the generally defined absorption edge of non-stoichiometric lithium niobate crystals

The ultraviolet absorption edges of LiNbO₃ crystals with different Li₂O contents and MgO doping concentrations were investigated. The generally defined absorption edges at absorption coefficient α=15 or 20 cm⁻¹ of all these crystals fit the Urbach rule perfectly. The origin of this absorption edges in non-stoichiometric LiNbO₃ crystals is attributed to the presence of Li vacancies.     

Ab Initio Calculations of Differential Cross Sections for Single Charge Transfer in ^3He^2＋ ＋ ^4He Collisions

The single charge transfer process in ^3He^2＋ ＋ ^4He collisions is investigated using the quantum-mechanical molecular- orbital close-coupling method, in which the adiabatic potentials and radial couplings are calculated by using the ab initio multireference single- and double-excitation configuration interaction methods. The differential cross sections for the single charge transfer are presented at the laboratorial energies E = 6 keV and lOkeV for the projectile ^3He^2＋. Comparison with the existing data shows that the present results are better in agreement with the experimental measurements than other calculations in the dominant small angle scattering, which is attributed to the accurate calculations of the adiabatic potentials and the radial couplings.     

Hydrogen Passivation Effect on Enhanced Luminescence from Nanocrystalline Si/SiO2 Multilayers

Nanocrystalline Si/SiO2 multilayers are prepared by thermally annealing amorphous Si/SiO2 stacked structures. The photoluminescence intensity is obviously enhanced after hydrogen passivation at various temperatures. It is suggested that the hydrogen trapping and detrapping processes at different temperatures strongly influence the passivation effect. Direct experimental evidence is given by electron spin resonance spectra that hydrogen effectively reduces the nonradiative defect states existing in the Si nanocrystas/SiO2 system which enhances the radiative recombination probability. The luminescence characteristic shows its stability after hydrogen passivation even after aging eight months.     

Negative Refraction and Near-Field Imaging of an Elliptical-Rod Photonic Crystal Slab in the Second Band

Negative refraction and imaging properties of the electromagnetic wave through a two-dimensional photonic crystal （PC） slab, which consists of a square lattice of elliptical dielectric rods immersed in the air background, is studied by the plane-wave expansion method and the finite-difference time-domain method. A point source placed in the vicinity of the PC slab can form a good-quality image spot through the PC slab for the incident frequencies within the second photonic band. The calculated result also shows that negative refraction occurs in this kind of PC slab.     

N掺杂锐钛矿TiO2光学性能的第一性原理研究

用平面波赝势方法(PWP)计算了N掺杂锐钛矿型TiO2前后的光学特性,即介电函数虚部ε2(w),光学吸收系数I(w)和反射率R(w).并从能带结构上解释了为什么掺N后锐钛矿型TiO2的光学谱在2.93,3.56和3.97 eV处相对掺杂前会出现3个峰值的原因.从光谱图上分析得出,掺杂后TiO2要发生红移现象,实验现象证实了这一结果.     

A novel scheme of label abstraction and erasion based on Fabry-Perot semiconductor optical amplifier

A novel label abstraction and erasion scheme based on a Fabry-Perot semiconductor optical amplifier (FP-SOA) is proposed for all-optical separation of the bit-serial label from payload and its performance is investigated by simulation. Important features of this scheme are that it does not make use of any high-speed electronics and only one device is needed. Using this scheme, label abstraction and erasion can be realized with the extinction ratio of 9.72 and 7.05 dB, respectively.     

Calculations of Rydberg energy levels for Ni ⅩⅧ using the weakest bound electron potential model theory

Martin expression about the quantum defect of single-valence atoms is extended to many-valence atoms by identifying the weakest bound electron (WBE) under the weakest bound electron potential model(WBEPM) theory. Six Rydberg series energy levels of 2p6np2P°1/2 (n ≥ 3), 2p6np2P°3/2 (n ≥ 3), 2p6nd2D3/2(n ≥ 3), 2p6nd2D5/2 (n ≥ 3), 2p6nf2F°5/2 (n≥4), and 2p6nf2F°7/2 (n ≥ 4) for Ni ⅩⅧ are calculated by this method. The calculated results are in good agreement with the experimental results.