X射线荧光光谱分析

评述了我国在2000年7月-2002年6月间X射线荧光光谱，包括粒子激发的X射线光谱的发展和应用，内容包括仪器研制、激发源、探测器、软件、仪器改造、仪器维护和维修、样品制备技术、分析方法研究和应用。     

HL-2A装置等离子体可见光成像系统

在HL-2A装置上研制了等离子体可见光成像系统,用于孔栏、偏滤器位形放电的诊断。该成像系统由彩色摄像机、观察窗和转向镜、广角收集和准直透镜组、采集卡和计算机组成。本文描述了系统的布局和各部件参数的匹配,报道了观测到的实验结果。等离子体成像系统能监视放电的整个过程,实时显示可见光辐射图形,特别在识别孔栏与偏滤器位形放电的诊断中发挥了重要作用,成为HL-2A装置放电的重要诊断手段。     

Electrical conductivity of polycrystalline films of p-sexiphenyl

In this work the results of DC conductivity measurements of polycrystalline p-sexiphenyl thin films are presented. The investigations concerned the effect of temperature, film thickness and electric field on the DC conductivity mechanism. The thickness of the investigated material varied from 0.2 to 2.5 μm. The measurements were carried out for different electrode polarities of the 0 -100 V voltage and at temperatures ranging from 15 to 325 K. Thin films of p-sexiphenyl were obtained by controlled vacuum sublimation on BK-7 glass substrate with gold and aluminium electrodes. Analyzing the obtained results we conclude that injection of the charge carrier from electrodes into the investigated material proceeds by thermionic emission and field emission and it is dependent on temperature and external electric field. The charge carrier transport is controlled by localized states (traps) in the forbidden energy gap. The activation energy calculated from formula ln I = f(1/kT) varied from kT for low temperature up to 1.0 eV.     

Study of Spectroscopic Properties of Yb-doped Calcium Fluorapatite

The spectroscopic performance of Yb-doped calcium fluorapatite (Yb:FAP) was assessed by measuring polarization absorption spectra, polarization emission spectra and fluorescence lifetime. The emission cross section has been evaluated using the absorption cross section and principle of reciprocity. The π polarization absorption and emission cross sections of Yb3+ in FAP are found to be substantially larger than those of other Yb-doped media. Favorable spectroscopic parameters show that Yb:FAP crystal is more desirable for many diode-pumped solid state laser application with low- and medium-power in the near future.     

Photo-atomic effect: Temperature dependence of the photodesorption of Na and from polymer surfaces

Alkali metals adsorbed to surface films of the polymer poydimethylsiloxane (PDMS) have been shown to exhibit a unique photodesorption behavior, characterized by a frequency threshold and high efficiency. In this work, the temperature dependence of the photodesorption yields of Na and Na ₂ from PDMS surfaces were measured between room temperature and 183 K. Over most of the temperature range, the yields exhibited an Arrhenius behavior characterized by thermal activation energies of 0.36 eV and 0.34 eV for Na and Na ₂ , respectively. These values are suggestive of a surface diffusion as one of the elementary steps in the photodesorption mechanism. Moreover, the similarity of the two values indicates that the same elementary step applies to the desorption of both Na and Na ₂ . Received 23 April 1999 and Received in final form 15 July 1999     

Structure and stability of the anatase TiO2 (101) and (001) surfaces

Well-defined (101) and (001) surfaces of anatase TiO₂ were studied for the first time by secondary-electron imaging and low-energy electron diffraction. Initially, both surfaces show a crystalline structure corresponding to the bulk anatase phase, buried under an atomically thin contamination layer. After mild sputtering with 500 eV Ne⁺ ions, we have observed a surface phase transition from tetragonal anatase to face-centered cubic titanium monoxide TiO. Subsequent annealing at 900 K restores the (1×1) anatase structure at the (101) surface. On the (001) surface, however, a (1×4) reconstruction appears. The unreconstructed structure can be recovered by exposing the surface to oxygen. These observations demonstrate the stability of the anatase surfaces and illustrate the feasibility of preparing and investigating clean surfaces of this technological important form of TiO₂.     

Enhancement of soft X-ray emission from a pinch plasma using a rotating plasma for pre-ionization

An experimental study on the enhancement of soft X-ray emission from a pinch plasma has been carried out by using a rotating plasma for pre-ionization. The rotating plasma is produced by a pulsed J×B cross-field discharge between coaxial electrodes, and subjected to a pinch discharge. Under an optimized discharge condition, it has been observed that UV emission of 251.6 nm (Ar III) soft X-ray intensity increases with increasing applied axial magnetic field B. At 400 G, the X-ray intensity is enhanced by a factor of 3 compared to that without the rotating plasma. It is considered that this result is due to the improved characteristics of the pre-ionization rotating plasma, which influences the uniformity and stability of subsequent pinch plasma.     

悬浮液进样-火焰原子发射光谱法测定米类粮食中的钾

将悬浮液进样技术应用于火焰原子发射光谱分析,成功地测定了大米,小米及高梁米中的钾,建立了快速测定钾的新方法。将样品磨细、制成琼脂悬浮液,为消除电离干扰,取适量悬浮液,加入ＮａＣｌ溶液,并制成试液。将试液喷入空气－乙炔火焰,用工作曲线法测定。     

包含伺服约束的非完整系统的Lie对称性与守恒量

利用代数方程和微分方程在无限小变换下的不变性,研究带有伺服约束的非完整系统的Lie 对称性.给出Lie对称性的确定方程、限制方程、结构方程,并给出守恒量的形式. 关键词： 非完整系统 伺服约束 Lie对称性 守恒量     

三维光子晶体中三能级原子的自发发射

研究了三维光子晶体中三能级原子自发发射的性质.由于各向异性色散关系,能带带边的态密度没有奇异性,局域场可以消失.在一定条件下弥散场会得到加强,并在辐射场中占主导地位.这些性质将与原子能级和能带带边的相对位置有关,且有别于各向同性色散关系的光子晶体中原子自发发射的性质. 关键词： 光子晶体 三能级原子 自发发射