惰性原子基团的研究

一般情况下,惰性气体不易与其他元素或本身发生化学反应.然而,英国Sussex大学的两位化学家 Poul Lethbridge 和 Tony stace制成了含有多至340个氪原子的原子基团或簇(Journal of Chemical Physics,vol.91,p.7685).这一结果填补了分子体系和体材料之间的空白.这种结构对研究催化作用很有意义. 制造原子簇的过程为:让气态氪通过一直径为200μm的小孔射入真空室.经过喷射冷却的氪原子相互碰撞,弱的范德瓦耳斯力,不断地使碰撞的原子聚集在一起,形成一定结构的基团.制成的基团原子数在10至340之间.研究人员先用电子束将基团离化,再用质谱仪分…     

Measurements of displacement and trapping force on micron-sized particles in optical tweezers system

A high-stability optical tweezers equipped with a high-precision measurement system of displacement and force is set up. The results show that this combination can be used to carry out quantitative measurements of small displacements and forces for micron-sized spheres. The precision of measurements has reached nanometers and piconewtons, respectively.     

Theoretical study of enhancement and suppression of the fluorescent spectra of dye molecules in a photonic crystal with a pseudogap

We have investigated the analytical forms of the photonic density of states (DOS) in a photonic crystal in the interested frequency regime according to the rule of state conservation in a photonic crystal with pseudogaps, which states that, if a valley of the DOS appears in some range of frequencies, it must be compensated for by increasing over some other ranges. By using a model DOS with a state-conservative photonic pseudogap, we have also investigated the enhancement and suppression of spontaneous emission of two-level atoms with different frequency positions and widths of emission spectra in a state-conservative electromagnetic reservoir; and the DOS-induced suppression, enhancement, narrowing and redshifting or blueshifting of spontaneous emission spectra are naturally obtained.     

二维非晶光子材料的缺陷态

应用多重散射方法计算了二维介质柱构成的非晶光子材料的缺陷态。在非晶光子材料中抽掉不同位置的圆柱会产生频率不同的缺陷模，但缺陷模的能量都是非常局域的，能量基本上集中在以缺陷波长1／3为半径的圆内。这表明非晶光子材料中形成的缺陷模不仅具有周期性光子晶体的缺陷模的强局域化特征，同时缺陷模更富于变化。     

二维LiNbO3非线性光子晶体

制备了周期为13.64 μm方形格子二维周期性极化的LiNbO₃，利用二阶准相位匹 配实现了波长为1.064μm二倍频，二次谐波的内部转换效率高达42％. 测量了二次谐波输出功率随晶体温度及入射光入射方向的变化，实验值与模拟计算一致. 制备二阶准相位匹配掩模板，解决了在制备一阶准相位匹配掩模板中遇到周期尺寸太小、数据量大的难题，同时还降低了因周期太小造成的极化难度. 关键词： 二维 准相位匹配 二次谐波     

十二重准晶光子结构中的负折射与成像

最近实验证明周期性的光子晶体中存在电磁波的负折射现象，并且观测到亚波长成像．然而，这些研究主要集中在剧期性结构中，对非周期结构的研究还没有相关的报道。文章报道了一种新的理论和实验结果：非周期性十二重准晶光子结构同样存在负折射，并且可以实现超透镜的远场成像。具有这些特性的光子准晶可以广泛的应用于光集成器件中。     

The Role of Periodicity in Enhanced Transmission through Subwavelength Hole Arrays

Two kinds of subwavelength hole arrays in metallic films are designed to verify the import, ant role of the periodicity in enhanced transmission of light. The measured optical spectra show that the quasiperiodic hole arrays exhibit an enhanced transmission peak centred at 707nm with a transmission intensity of about 20%, while no plasmon resonance peak is found for the amorphous hole arrays. When the hole diameter decreases in the quasiperiodic structure, the position of the transmission peak shifts slightly, and the transmittance drops, These phenomena indicate the important role of the long-range structural order （particularly the periodicity） in assisting the coupling of incident light wave with the surface plasmon modes of the metallic structures.     

周期极化LiNbO3晶体中电极布置对反转畴扩张的影响

利用外加电场极化的方法,分别研究了三种不同方式布置的极化电极对C向切割LiNbO3晶体极化反转畴扩张的影响.实验结果表明在相同极化条件下,当极化电极长度方向与六边形反转畴一对边呈90°和0°角时,极化扩张速度分别为0.089μm/ms和0.011μm/ms.实验结果揭示,为了有效地控制极化占空比,在制备一维准相位匹配LiNbO3晶体时应避免极化电极与六边形反转畴壁中一对边呈90°的情况.     

Fabrication of Alumina Films with Three-Dimensional Ordered Macropores by Self-Assembly of Binary Colloidal Spheres

We present a new process to obtain a three-dimensional ordered macroporous structure (3DOM). The 3DOM films were fabricated using a coassembly of monodispersed polystyrene spheres and alumina hydroxide sols in aqueous suspensions on a vertical substrate followed by a calcination treatment. The 3DOM film structure, quality and morphology have been characterized by scanning electron microscopy and transmission spectra.     

PbCl2分子的光解离

用YAG激光的四次谐波光解离PbCl₂分子。实验确认了这种光解过程是双光子过程。通过对激光诱导荧光的测量,发现这一光解过程造成了Pb原子的亚稳态6p^{2 3}P₂与基态6p^{2 3}P。间的粒子数反分布。同时观察到基于6p^{2 3}P₂能级的受激共振辐射及受激喇曼散射。 关键词：