多元体系中谐波对EXAFS振幅的影响

本文给出了多元体系中谐波对EXAFS振幅的影响的计算方法,并以实例计算和测量了这种影响,两者结果相符。 关键词：     

磁尾中性片处一种反常电阻机制

本文在平板模型近似下探讨了磁尾中性片非绝热离子逆磁漂移不稳定性及其反常电阻。该不稳定性是由非绝热离子逆磁漂移激发的,非绝热离子的轨道漂移共振大大增强了不稳定性强度。相应的反常电阻率为10⁴(Q·m)量级,与触发磁尾磁场重联所需电阻值相近。     

Cu1-xAux固溶体原子近邻结构的EXAFS研究

本文用扩展X射线吸收精细结构谱(EXAFS)研究了Cu_1-xAu_x固溶体中Cu,Au原子近邻结构.文中分别给出了不同成分时Cu-Cu,Au-Au和Au-Cu 原子对间距,发现它们与成分有着各自不同的依赖关系.表明了Cu_1-xAu_x固溶体中结构畸变的特征.由各原子对的间距计算出的合金平均原子间距随成分的变化与X射线衍射测量的结果一致,对Vegard定律有正偏离.文中还讨论了原子近邻间距的变化对这种偏离的影响.结果也表明,Cu_1-xAu_x固溶体中Cu原子有较大的无序度.此外,文中还对EXAFS数据处理和误差分析做了仔细的考虑和一些新的尝试.     

空间r射线谱(Ⅱ)

2　r射线谱的功用 (1)耀斑中粒子相互作用模型的推断 太阳耀斑中粒子相互作用模型有厚靶模型和薄靶模型两种.这里的厚靶和薄靶与核物理、粒子碰撞物理中的厚、薄靶的含义有相似之处,这就是厚靶粒子经相互作用后全被吸收,而薄靶则有部分粒子逸出.在耀斑模型中,就含能粒子的情况来说,薄靶模型是指加速粒于由于碰撞和核互作用造成的能量损失正好为连续加速机理带来的能量输入所平衡,即在相互作用区有含能粒子逸出,而厚靶模型则是指粒子在太阳大气中被阱获和慢化,并且全部粒子都经历相互作用而无逸出.就电磁辐射的情况来说(X射线、r射线),厚靶…     

晶格的力学稳定性研究

推导出利用embedded-atommethodEAM势表达的力学稳定性判据给出了相应的数值方法,并且提出了确定势函数的适用范围的理论判据。根据该理论肯定了A.Voter等给出的镍原子间的EAM势的可靠性,并计算了镍单晶体的力学性质。计算表明:单轴外力沿[100]方向加载在镍单晶体上,在压应力作用下,晶体结构发生转变,产生两个不稳定的新结构相bcc和bct相在张应力作用下,镍单晶发生均匀形变,当形变量达10.51％时材料断裂,相应的理论拉伸强度值为1.46×10~(11)dyn·cm~(-2)。由这些计算 关键词：     

现应将宇宙线从电磁波谱中删去

现应将宇宙线从电磁波谱中删去方正知（中国科学院空间科学与应用研究中心北京１０００８０）自２０世纪初发现宇宙线（ＣｏｓｍｉｃＲａｖｓ，Ｕｌｔｒａｓ－ｔｒａｈｌｕｎｇ）以来直至１９３２年以前，一直认为此种射线本身系由类似γ射线的光子所组成，只是其波长比γ...     

A MICROSCOPIC MECHANISM OF LOW TEMPERATURE HELIUM RELEASE

⁴He ions of various energies and at various doses were implanted into three kinds of samples: TiH₂ films, high purity Ti pieces as-received and after hydrogenation. Thermal release of helium was monitored in situ by proton-enhanced backscattering. Low-temperature helium release was observed at T≤573K. Single jump model was used to calculate the active energies for the release. Based on the observations, a mechanism of helium cluster vacancy complex (He_mV_n-V_i) for low temperature helium release is proposed.     

DIFFUSIVE AGGREGATION ON ION IMPLANTED THIN FILMS

Diffusive aggregation on-ion implanted thin films is studied. It is revealed that aggregation is realized mainly by atoms or clusters in the film matrix. The implanting ions play the role of triggering them into motion and supplying the kinetic energy for their diffusion. The aggregation process is characterized by finite density of aggregating particles, random triggering, and limited diffusion distance. The aggregate observed shows scaling or fractal property.     

A STUDY OF THERMAL DESORPTION OF HELIUM FROM HIGH-PURE α-Ti AND HYDROGENATED Ti SAMPLES

Helium ions have been implanted into highly pure α-Ti and hydrogenated Ti samples with energy of 140keV and at dose of 5.2×10¹⁷He·cm^-2. The retained amount and depth pro-files of helium in the samples were determined by means of proton-enhanced-backscattering (PEBS) at room temperature. The changes of He peaks during isochronical annealing at 100, 200, 300℃,… were monitored in-situ by PEBS for groups of samples. The process of temperature ramping was not stopped until He peaks almost disappeared and hence the release curves were obtained. It was found that ～ 60% of helium was released at 200℃ for high-pure α-Ti samples, whereas massive release occurred at 300℃ for the samples with H/Ti=0.9 and at 350℃ for the samples with H/Ti=0.2. The mechanism of He release and the effect of hydrogen were also discussed.