The influence of atomic vibrations on x-ray absorption near edge structure (XANES) is calculated by assuming that vibrational energies are small with respect to the instrumental resolution. The resulting expression shows that, at the K-edge, vibrations enable electric dipole transitions to 3s and 3d final states. The theory is applied to the K-edge of Al in Al2O3 corundum and of Ti in TiO2 rutile and compared with experiment. At the Al K-edge, sizeable transitions towards 3s final states are obtained, leading to a clear improvement of the agreement with experimental spectra. At the Ti K-edge, electric dipole transitions towards 3d final states explain the temperature dependence of the pre-edge features.
Investigation on Anharmonicity, Vibrational Anisotropy and Thermal Expansion of an Amorphous Ni$_{46}$Ti$_{54}$ Alloy Produced by Mechanical Alloying using Extended X-ray Absorption Fine Structure
提出了一种利用基于累积膨胀的扩展X射线吸收精细结构(EXAFS)分析得到的平行和垂直于原子间键的相关均方相对位移(MSRD)研究非谐性、振动各向异性和热膨胀的方法,并将其应用于机械合金化制备的非晶态Ni $_{46}$ Ti $_{54}$合金。通过在不同温度下对Ni和Ti K边的EXAFS测量,获得了$\text{MSRD}_\parallel$、$\text{MSRD}_\perp$和实分布函数$\varrho_{ij}(r,T)$的累积量$C_1^*$、$C_2^*$和$C_3^*$的热行为,以及与平行和垂直运动有关的爱因斯坦温度和频率,提供了关于原子间势的非谐性的信息。振动各向异性以及垂直运动对总无序和热膨胀的贡献。
Investigation on Vibrational, Optical and Structural Properties of an Amorphous Se$_{0.80}$S$_{0.20}$ Alloy Produced by Mechanical Alloying
用Raman光谱、X射线衍射、扩展X射线吸收精细结构(EXAFS)和光学吸收光谱研究了机械合金化法制备的非晶态Se $_{0.80}$ S $_{0.20}$合金,并对其总结构因子和EXAFS数据进行了反向蒙特卡罗模拟。它的振动模式,光学间隙和平均原子间距离和平均配位数的结构特性进行了测定和比较,发现为非晶硒$_{0.90}$ S $_{0.10}$合金。结果表明,配位数,原子间距离和间隙能量依赖于硫浓度。
Effects of Interference between Energy Absorption Processes of Molecule and Surface Plasmons on Light Emission Induced by Scanning Tunneling Microscopy
Revisiting the configurations of hydrogen impurities in SrTiO3: Insights from first-principles local vibration mode calculations
Advanced Technology Research Institute of Taihu Photon Center, School of Physical Science and Technology, Suzhou University of Science and Technology(太湖光子中心先进技术研究院,苏州科技大学物理科学与技术学院)
研究通过第一性原理局部振动模式计算,重新审视 SrTiO3 中氢杂质的配置及振动特性,发现氢空位复合物与 Sr 空位复合物的振动频率与实验红外吸收带匹配,揭示氢相关复合物对 STO 电子性质的重要性。
Fingerprints of carbon defects in vibrational spectra of gallium nitride (GaN) consider-ing the isotope effect
Leibniz-Institut für Kristallzüchtung (IKZ)(莱布尼茨晶体生长研究所);Center for Computational Materials Science, United States Naval Research Laboratory(美国海军研究实验室计算材料科学中心);Institute of Experimental Physics, TU Bergakademie Freiberg(弗莱贝格矿业技术大学实验物理研究所);Ferdinand-Braun-Institut (FBH)(费迪南德·布劳恩研究所);Institute of Solid State Physics, Technische Universität Berlin(柏林工业大学固体物理研究所);Technische Physik, University of Würzburg(维尔茨堡大学技术物理系)
Analysis of the excited-state absorption spectral bandshape of oligofluorenes
本文报道了两种低聚芴衍生物在稀溶液中的超快瞬态吸收光谱。这些光谱显示清晰的电子振动结构,我们分析严格使用依赖于时间的吸收形式主义提取的主要激发态振动正常模式的频率,耦合到电子跃迁,较高的说谎激发态的构型位移,和重组能量。我们可以使用频率为450 cm(二聚体)或400 cm $^{-1}$(三聚体)和1666 cm $^{-1}$的两个完全对称的振动模式来模拟激发态吸收光谱。基态吸收的重组能量是相当不敏感的低聚物长度在230毫电子伏。然而,低聚芴二聚体和三聚体之间的激发态吸收从58到166 meV。基于先前的理论工作[Shukla等人,\textbf{67},245203(2003)],我们将吸收光谱归属于从$1B_u$激发态到更高的$mA_g$态的跃迁,并发现激发态跃迁能量相对于基态跃迁能量与这里研究的两种低聚物的理论预测非常一致。这些结果和分析允许在$π$共轭聚合物,这是作为在固态的有机半导体的普遍感兴趣的主题的激发态吸收的性质的深刻理解。