单量子双能级系统和双态系统关联函数的研究

以具有简单三能级结构染料分子的单量子系统为研究对象,用带有边界条件的速率方程来反映低功率单色连续激光激励下单分子发射荧光的动力学过程.该方法可以通过时间分辨光子探测获得处理单分子动力学随机过程.研究给出了一种通过求解反映单量子系统动力学过程的物理量——延迟函数计算关联函数的方法,并给出了双能级系统和双态系统延迟函数和关联函数的具体表达式.研究表明,在实际测量中只要获得关联函数曲线,就可以通过数据拟合计算出分子跃迁的动力学参量.     

Ion debris mitigation from tin plasma using ambient gas,magnetic field and combined effects

Mitigation of energetic ions from laser produced tin plasma is one of the principal issues in the development of an extreme ultraviolet lithographic light source. We explored the possibility of using an ambient gas and/or a magnetic field for controlling the energetic ions from tin plasma. Hydrogen, helium and argon gases provide good transmission to 13.5 nm and are found to be an effective stopper for tin ions. Absorption of in-band radiation limits the density of gas below levels needed to completely protect optics. Tin ion ranges in buffer gases were estimated using the Monte Carlo simulation code SRIM and compared with experimental results. The presence of a moderate transverse magnetic field of 0.64 T slowed the propagation of fast moving tin ions but failed to stop them. The synergistic effect of a combination of magnetic field and an ambient gas is found to be very promising for mitigating tin ions without exceeding EUV gas absorption limits. PACS 42.72.Bj; 52.50.Jm; 52.55.Jd; 52.70.kz     

Transient thermal characterization of micro/submicroscale polyacrylonitrile wires

In this work, the thermal diffusivity of single polyacrylonitrile (PAN) wires with diameters from 4.62 μm down to 324 nm is measured by using our recently developed transient electro-thermal technique. The wires span from 23 μm to 126.2 μm in our measurement. Since PAN wires are dielectric, a thin Au film is coated on the surface of the wires to make them conductive. In the experiment, a step current (with ∼2 μs rising time) is fed to the sample. The sample is heated and takes a certain time to reach its steady thermal state. The temperature rising response of the sample is sensed by measuring the resistance change of the thin Au coating. From the average temperature evolution of the sample, the thermal diffusivity can be extracted. Three PAN wires with different diameters are synthesized using the electro-spinning technique and are measured to obtain their thermal diffusivities (around 1.53×10^-7 m²/s), which are slightly smaller than the bulk value. PACS 65.80.+n; 66.30.Xj; 44.10.+i     

吡啶/氧气/氩气火焰中氮宾的鉴别和化学研究

利用可调谐同步辐射真空紫外光电离和分子束质谱技术探测和鉴别了低压预混层流吡啶/氧气/氩气火焰中的三重态氮宾．通过测量光电离效率谱和理论计算确定了氮宾的电离能．结果表明氮宾的基态为三重态，其第一和第二绝热电离能分别为8.04和9.15§0.05 eV．另外，根据已探测到的物种提出了氮宾的形成和消耗通道．氮宾是燃烧化学中探测到的第一个含氮双自由基，因此，在吡啶火焰的动力学模型中应该将它考虑进去．     

Discussion again of the magnetic and transport property of Ag-doped LaMnO3

Samples La_1−aAg_aMnO₃ (0.05?a?0.50) were sol–gel fabricated. A part of Ag was found to dissociate and run off the samples in sintering process when sintering temperature exceeds 700 °C, resulting in a composite of La_1−xAg_xMnO₃ and MnO₂/Mn₂O₃. The magnetic and transport properties of the composite have been studied. The sample with the nominal composition La_0.7Ag_0.3MnO₃ was found to show the greatest magnetoresistance in the sample group. Detailed analysis on average Mn valence reveals a composite of (La_0.985Ag_0.015MnO₃)_0.776[(MnO₂)_0.590(Mn₂O₃)_0.410]_0.224. Its MR ratio at room temperature exceeds 24% under a field of 1.8 T. A conductivity leap has been observed around a=0.30. It suggests a kind of field-induced fluctuation in percolation in the samples investigated.     

Surface modification of multi-walled carbon nanotubes by O2 plasma

The surface modification of multi-walled carbon nanotubes (MWCNTs) by O₂ plasma was carried out in this study. In order to achieve a relatively homogeneous treatment of MWCNTs powder, a rotating barrel fixed between the two discharge electrodes was used. The effect of plasma treatment parameters, such as power, time, and positions of samples (inside and outside the barrel), on the morphology and structure of MWCNTs surface was systematically analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results showed that the direct discharge (outside the barrel) could result in not only a quick grafting of polar functional groups but also an easy damage of MWCNTs after longer time, particularly under intensive power. It was found that the surface of MWCNTs powder might be changed in three steps—expansion (loosed structure formed), peel off and oxidization with increasing of treatment time during the irradiation. In this way, a complete purification of MWCNTs powder could be finished within 30 min via plasma treatment. Our work suggested that plasma treatment could be a simple and nonpolluting method for a large scale purification of MWCNTs.     

开边界条件下一类新Hubbard模型的精确解

用坐标Bethe ansatz方法详细研究了开边界条件下一类新Hubbard模型的可积性问题. 得到了系统的能谱、可积边界条件和Bethe ansatz方程.     

MCeO3：Eu^3＋（M=Sr，Ba）的合成及发光性质研究

利用高温固相反应法合成了Eu^3＋掺杂的MCeO3（M=Sr，Ba）发光粉末样品，采用X射线衍射技术和荧光光谱等测试手段分别对其物相组成和发光性质进行了研究。X射线衍射结果显示，Eu^3＋离子容易替代MCeO3晶格中M^2＋离子的位置。荧光光谱测试结果表明，Eu^3＋掺杂的SrCeO3和BaCeO3样品在紫外波段存在着非常宽的吸收带，峰值分别位于311和320nm左右，它们属于Ce^4＋-O^2-的电荷迁移带，SrCeO3和BaCeO3基质与Eu^3＋离子之间存在着能量转移。在MCeO3：Eu^3＋样品中，Eu^3＋的发射主要来自于^5D0激发态能级，其中以磁偶极跃迁^5D0-^7F1发射强度为最大；此外样品中还存在着较高的^5D1激发态能级的辐射跃迁。SrCe03：EU^3＋样品的发射强度远大于BaCeO3：EU^3＋样品。     

Self-assembly of 5-octadecyloxyisophthalic acid and its coadsorption with terephthalic acid

The structure of the self-assembled monolayer of pure 5-octadecyloxyisophthalic acid (5OIA), and the coadsorption monolayer of 5OIA and terephthalic acid, is investigated using scanning tunneling microscopy (STM) at the liquid-solid interface. 5OIA self-assembles into a monolayer comprised of different structures. For the major phase, 5OIA molecules alternately pack with opposite enantiotopic faces in a lamella, giving lamellae with a chain-to-trough angle of ∼88°. Two adjacent lamellae are assembled together by a hydrogen-bonding network between two carboxylic acid groups from each lamella. In the self-assembled monolayer of the mixture solution of 5OIA and terephthalic acid, 5OIA molecules coadsorb with terephthalic acid and therefore form two stoichiometric multi-component domains. Each domain has a molar ratio of 2:1 for 5OIA and terephthalic acid. For each component (5OIA or terephthalic acid), the two coadsorption structures exhibit opposite chirality.     

Electronic structure and site occupation for the intermediate phase of LaNi4.5Al0.5Hy

The crystal structure, electronic structure and hydrogen site occupancy of LaNi_4.5Al_0.5H_y intermediate phase (y=2.0, 3.0, 4.0) have been investigated using the full-potential linearized augmented plane wave (FLAPW) method. For the first time we analyzed the interstitial site occupation of hydrogen atoms. The H atoms were found to prefer the 6m, 3f and 12n sites, while no 4h sites were occupied. A narrowed Ni-d band is found due to the lattice expansion: the total DOS at E_F increases with y, which indicates that the compounds become less stable. The interaction between Al and Ni, with H plays a dominant role in the stability of LaNi_4.5Al_0.5H_y intermediate phase. The smaller the shift of E_F towards the higher energy region, the more stable the compounds will be. Our results are compared with experimental data and discussed in the light of previous works.