脉冲激光偏振方向对氮分子高次谐波的影响——基于含时密度泛函理论的模拟

采用含时密度泛函方法,结合赝势模型和电子交换相关作用的广义梯度近似,模拟了氮分子在超强飞秒激光脉冲作用下的高次谐波产生现象,并研究了激光脉冲偏振方向对氮分子高次谐波的影响.结果表明氮分子的高次谐波谱具有典型原子谐波谱的特征;谐波谱强度随着θ(激光偏振方向与分子轴向夹角)的增大而减小.这与J.Itatanl在Nature上报道的实验结果基本一致.     

SiO2-羟基表面上金属原子的第一性原理研究

采用第一性原理方法研究了SiO2-羟基表面上几种金属原子的吸附性质,发现In和Ga在SiO2-羟基表面上的结合很弱,而Fe,Co,Ni在该表面上与Si,O形成强的化学键.等势能面和扩散势垒计算表明In(Ga)的扩散激活能只有0.1-0.3 eV,表明这两种原子容易在表面上扩散.这些结果可以定性地解释纳米合成中的一些实验现象.     

Spin tunneling properties in mesoscopic magnets: effects of a magnetic field

The tunneling of a giant spin at excited levels is studied theoretically in mesoscopic magnets with a magnetic field at an arbitrary angle in the easy plane. Different structures of the tunneling barriers can be generated by the magnetocrystalline anisotropy, the magnitude and the orientation of the field. By calculating the nonvacuum instanton solution explicitly, we obtain the tunnel splittings and the tunneling rates for different angle ranges of the external magnetic field ( θ _H = π/2 and π/2 < θ _H < π). The temperature dependences of the decay rates are clearly shown for each case. It is found that the tunneling rate and the crossover temperature depend on the orientation of the external magnetic field. This feature can be tested with the use of existing experimental techniques. Received 12 March 2001 and Received in final form 18 October 2001     

磁控溅射ZnO薄膜的成核机制及表面形貌演化动力学研究

利用原子力显微镜分析了ZnO薄膜在具有本征氧化层的Si(100)和Si(111)基片上的表面形貌 随沉积时间的演化. 通过对薄膜生长形貌的动力学标度表征，研究了射频反应磁控溅射条件 下，ZnO薄膜的成核过程及生长动力学行为. 研究发现，ZnO在基片表面的成核过程可分为初 期成核阶段、低速率成核阶段和二次成核阶段. 对于Si(100)基片，三个成核阶段的生长指 数分别为β₁=1.04，β₂=0.25±0.01，β₃=0.74；对 于Si(11 关键词： ZnO薄膜 磁控溅射 生长动力学 成核机制     

Raman spectroscopic study of ceramic Sr2Bi4Ti5O18

Raman spectra of ceramic Sr2Bi4Ti5O18 （SBTi5） are reported to consist of four different Raman bands. Temperature-dependent spectra reveal the relationship between the lattice vibration and the material＇s structure. There appears a relatively large change in structure of the material at about 273K, The anharmonic potential of the material has a great influence on its phonon mode full width at half maximum （FWHM）, which can be expressed by a function of temperature. Theoretical fittings of the FWHMs for the two modes at around 312 cm^-1 and 464cm^-1 indicate that the latter phonon mode is more anharmonic than the former one.     

计算全息图产生的锥面波在激光准直中的应用

本文提出了用计算全息图产生锥面波的方法.将全息图置于激光光路中,它的衍射图样中心在空间形成了一条准直线.文中对锥面波的传播、准直精度及准直距离作了理论分析,给出了实验结果.     

瑞香狼毒防治仓储害虫活性物质的研究

瑞香狼毒 (ＳｔｅｌｌｅｒａｃｈａｍｅｊａｓｍｅＬ .)又名断肠草 ,为瑞香科狼毒属植物。瑞香狼毒在我国大部分地区均有分布 ,盛产于四川、河北、山西等地。其性苦、平、辛、有毒 ,有逐水、祛痰、破积、杀虫之功效。据文献报道 ,瑞香狼毒除了可作为中药外 ,还可以用来防治菜青虫、蚜虫、松毛虫 ,甚至可以用来杀蚊、驱蝇、灭蛆等。作者前期工作曾以瑞香狼毒根为材料 ,初步研究了根及根粉粗提物对米象、玉米象、谷蠹的防治效果。发现瑞香狼毒对米象、玉米象、谷蠹等仓储害虫均有较好的防治功效[1] 。本文以米象为试虫 ,以生物活性跟踪法对瑞…     

拟南芥胚的不同区域对MeV离子辐照的响应

利用不同能量的质子在大气环境中辐照拟南芥的含水种子，能量从1.1MeV到6.5MeV.根据模拟计算结果，相应能量的离子对种子的损伤区域分别为胚的浅层、胚的一半和整个胚.本实验中，具有较高能量的质子可以完全均匀地作用于拟南芥生长、发育及遗传密切相关的胚茎端分生组织，而能量较低的质子则不能直接作用于茎端分生组织.实验所用质子注量范围为4×10⁹ions/cm²—1×10¹⁴ions/cm².实验结果显示，虽然拟南芥种子的发芽率和幼苗存活率随离子注量增加都呈现下降的趋势，但对应于不同的胚损伤区域，即在不同的入射质子能量条件下，注量曲线具有各自的特征.实验结果显示，拟南芥种子中除了胚茎端分生组织作为对离子辐照敏感的辐射主靶外，茎端分生组织之外的胚区域可能作为离子辐射次靶，影响到最终的辐射生物学效应. 关键词： 离子辐照 拟南芥 胚区域 生物效应     

Darboux transformation and solitons of Yang-Mills-Higgs equations in R2,1

The Darboux transformations for soliton equations are applied to the Yang-Mills-Higgs equations.New solutions can be obtained from a known one via universal and purely algebraic formulas. SU(N) soliton solutions are constructed with explicit formulas. The interaction of solitons is described by the splitting theorem:each p-soliton is splitting into p single solitons asymptotically as t →±∞.     

COMPLETE EXTREMAL SURFACES OF MIXED TYPE IN 3-DIMENSIONAL MINKOWSKI SPACE

ＣＯＭＰＬＥＴＥＥＸＴＲＥＭＡＬＳＵＲＦＡＣＥＳＯＦＭＩＸＥＤＴＹＰＥＩＮ３－ＤＩＭＥＮＳＩＯＮＡＬＭＩＮＫＯＷＳＫＩＳＰＡＣＥ￥ＧＵＣＨＡＯＨＡＯ（ＩｎｓｔｉｔｕｔｅｏｆＭａｔｈｅｍａｔｉｃｓ，ＦｕｄａｎＵｎｉｖｅｒｓｉｔｙ，Ｓｈａｎｇｈａｉ２００...