以新型原子距边矢量ν估计和预测烷烃核磁共振碳谱(13C NMR)化学位移(CSC)

系统研究了核磁共振碳谱与化学位移和规律,以及分子拓扑指数在定量[结]构[波]谱关系（QSSR）中的应用. 本文基于分子路径长度矢量p=（P\-1, P\-2, P\-3,\:, P\-m）与分子中原子相互作用, 提出了一种新型原子距边矢量并发现它与烷烃13C NMR 化学位移有良好线性相关性, 回归方程及其统计参数为: CSC=aν+ap\-3=∑m\-j=0a\-jν\-j+a\-10p\-3=a\-0(ν\-0=1)+a\-1ν\-1+a\-2ν\-2+a\-3ν\-3+a\-4ν\-4+bP\-3, R>0.990, EV=94.5%, RMS<0.772, F=49.069-3513.18,结果良好.     

Lifetime Measurement of the Metastable 23 P 0 State in Helium-like 197Au

Hyperfine Interactions - The determination of atomic lifetimes offers the possibility to investigate various aspects of the atomic structure. In the case of helium-like 197Au with nuclear spin 3/2,...     

Structure determination of Pb/Ge(111)-β-(√3 × √3)R30° by dynamical low-energy electron diffraction analysis and first-principles calculation

We have determined the atomic structure of the Pb/Ge(111)-β-(√3 × √3)R30° surface, which was shown to exhibit a large Rashba spin splitting in a metallic surface state by dynamical low-energy electron diffraction analysis. The Pb coverage for the optimized atomic structure is 4/3 with one Pb atom located at every third H(3) site of the bulk-truncated Ge(111) surface and the other three near the T(1) sites but slightly displaced towards the T(4) sites. The determined atomic structure agrees well with the energetically optimized one obtained from the first-principles calculation. The calculation also revealed that the potential for the Pb atoms on the H(3) sites is very soft along the surface normal, suggesting that their vertical position is distributed within a range of about 0.2-0.3 ?. The previously proposed phase transition associated with the surface melting is discussed.     

介质阻挡放电氢等离子体中氢原子浓度的光谱诊断

在化学气相沉积功能材料等离子体刻蚀及表面处理等过程中, 氢原子起着非常重要的作用。文章详细论述了利用发射光谱技术诊断氢原子的基本原理,以氩气作为内标对介质阻挡放电氢等离子体中的氢原子浓度进行了定量的诊断,研究了氢原子浓度、氢分子解离率随气压的变化规律。发现在0.32到5.1 kPa气压范围内,氢分子的解离率由5.2%下降到0.089%,相应的氢原子浓度由4.9×1015·cm-3下降到1.3×1015·cm-3。文章还研究了氢Balmer系以及氩(750.4 nm)谱线的发射强度随气压、放电电压、频率等放电参数的变化规律。     

Energy bands of atomic monolayers of various materials: Possibility of energy gap engineering

The mobility of graphene is very high because the quantum Hall effects can be observed even at room temperature. Graphene has the potential of the material for novel devices because of this high mobility. But the energy gap of graphene is zero, so graphene cannot be applied to semiconductor devices such as transistors, LEDs, etc. In order to control the energy gaps, we propose atomic monolayers which consist of various materials besides carbon atoms.To examine the energy dispersions of atomic monolayers of various materials, we calculated the electronic states of these atomic monolayers using density functional theory with structural optimizations. The quantum chemical calculation software Gaussian 03 was used under periodic boundary conditions. The calculation method is LSDA/6-311G(d,p), B3LYP/6-31G(d), or B3LYP/6-311G(d,p).The calculated materials are C (graphene), Si (silicene), Ge, SiC, GeC, GeSi, BN, BP, BAs, AlP, AlAs, GaP, and GaAs. These atomic monolayers can exist in the flat honeycomb shapes. The energy gaps of these atomic monolayers take various values. Ge is a semimetal; AlP, AlAs, GaP, and GaAs are indirect semiconductors; and others are direct semiconductors.We also calculated the change of energy dispersions accompanied by the substitution of the atoms. Our results suggest that the substitution of impurity atoms for monolayer materials can control the energy gaps of the atomic monolayers.We conclude that atomic monolayers of various materials have the potential for novel devices.     

Calculations of Rms Velocities of Atomic Vibrations in the Mossbauer Experiment

To study mechanical and physical properties of solid bodies, it is important to know the behavior of rms velocities of atomic vibrations, especially accompanying changes in the ambient temperature. Therefore, we investigate binary iron alloys in the vicinities of phase transition temperatures using Mossbauer spectroscopy. The rms velocities of atomic vibrations demonstrate that 3d-3p direct chemical bonds for Si and 3d-4p direct chemical bonds for Ge are broken (formed) at the phase transition temperature; as a consequence, the velocities of atomic vibrations sharply increase.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 62–64, April, 2005.     

Atom-molecule collisions in an optically trapped gas

Cold inelastic collisions between confined cesium (Cs) atoms and Cs2 molecules are investigated inside a CO2 laser dipole trap. Inelastic atom-molecule collisions can be observed and measured with a rate coefficient of approximately 2.6 x 10(-11) cm3 s(-1), mainly independent of the molecular rovibrational state populated. Lifetimes of purely atomic and molecular samples are essentially limited by rest gas collisions. The pure molecular trap lifetime ranges 0.3-1 s, 4 times smaller than the atomic one, as is also observed in a pure magnetic trap. We give an estimation of the inelastic molecule-molecule collision rate to be approximately 10(-11) cm3 s(-1).     

Natural Bond Orbital(NBO),Natural Population Analysis and Mulliken Analysis of Atomic Charges of 4-Amino-3-Phenylbutanoic Acid

The Molecular Structure of 4-Amino-3-phenylbutanoic acid conformers have been studied in the gas phase. Natural Bond Orbital Analysis (NBO) and Mulliken analysis of atomic charges of 4-Amino-3-phenylbutanoic acid have been performed by DFT level of theory using B3LYP/6-311++G(d,p) basis set. The atomic charges, electronic exchange interaction and charge delocalization of the molecule have been performed by Natural Bond Orbital(NBO) analysis and Natural Population Analysis(NPA) have been constructed at B3LYP/6-311++G(d,p) level.     

Experimental evidence of excited multicharged atomic fragments coming from laser-induced coulomb explosion of molecules

Direct experimental evidence is presented for the production of excited multicharged atomic fragments in the laser-induced Coulomb explosion of molecules. The comparison of the fluorescence signals of several atomic and molecular species shows that the excited fragments come from transient excited multicharged molecules. The atomic fluorescence spectra recorded with NH3, N2, and N2O, in the 50-120 nm wavelength range, show that the excitation increases noticeably from NH3 to N2O. This effect is interpreted in terms of the initial electronic configuration, which favors a stronger excitation when the electronic density is more delocalized on the molecular nuclear structure.     

Nucleation and submonolayer growth of C60 on KBr

Noncontact atomic force microscopy has been applied to the prototypical molecule-insulator system C60 on KBr to study nucleation and submonolayer growth. Overview images reveal an island growth mode with unusual branching structures. Simultaneous molecular and atomic resolution on the C60 and KBr surfaces, respectively, was obtained revealing a coincident 8x3 superstructure. Also, a 21+/-3 pm apparent height difference was observed in atomic force microscopy topographies between some first layer molecules. One of the initial nucleation sites of the C60 islands was determined by observation of loosely bound molecules at kink sites in monatomic KBr steps, in conjunction with the observation that islands form preferentially at step edges.     

一种新型原子共振滤光器研究

报道Rb原子法拉弟共振滤光器(AFROF)的理论与实验研究.考虑Rb原子超精细结构的塞曼效应,对Rb-AFROF的传输特性进行理论分析,实验观测了Rb-AFROF的工作频率、通带宽度随外磁场和气室温度的变化关系.测量表明,Rb-AFROF传输效率～50%,带宽小于3GHz,最小探测光强～0.1μW.     

3C-SiC(001)-(2×1)表面原子与电子结构研究

采用广义梯度近似的密度泛函理论方法计算了3C-SiC（001）-（2×1）表面的原子及电子结构．计算结果表明,3C-SiC（001）-（2×1）表面为非对称性的Si二聚体模型,其二聚体的Si原子间键长为0.232 nm．电子结构的计算结果表明,在费米能级处有明显的态密度,因此3C-SiC（001）-（2×1）表面呈金属性．在带隙附近存在四个表面态带,一个位于费米能级附近,一个位于费米能级以上5 eV处,另外两个位于费米能级以下的价带中． 关键词： 碳化硅 密度泛函理论计算 原子结构 电子结构     

Eötvös bounds on couplings of fundamental parameters to gravity

The possible dependence of fundamental couplings and mass ratios on the gravitational potential has been bounded by comparing atomic clock frequencies over Earth's elliptical orbit. Here we evaluate bounds on such a dependence from E?tv?s-type experiments that test the weak equivalence principle, including previously neglected contributions from nuclear binding energy. We find that variations of fundamental parameters correlated with the gravitational potential are limited at 10(-8)-10(-9), an improvement of 2-3 orders of magnitude over atomic clock bounds.     

中性原子的表面双磁光阱及其应用

提出了一种新的采用载流导线的表面双磁光阱(MOT)方案(即双U型导线磁光阱方案)。通过改变中间U型导线中的电流大小,即可将一个双磁阱连续地合并为一个单磁阱,反之亦然。详细计算和分析了上述双U型载流导线磁光阱方案的磁场及其梯度的空间分布,研究发现当导线中的电流为600 A,z方向均匀偏置磁感应强度为-4.0×10-3 T时,双U型导线方案产生的两个磁阱中心的磁场梯度约为1.5×10-3~2.5×10-3 T/cm,结合通常制备磁光阱时所用的三维粘胶(Molasses)光束即可在基底表面附近形成一双磁光阱。理论分析表明在弱光近似下,每个磁光阱中所能俘获的85Rb原子数约为106 量级,相应的磁光阱温度约为270μK。由于双磁光阱可以独立制备,所以双U型导线方案特别适用于制备双样品磁光阱,并用于研究双原子样品的冷碰撞性质。     

Optical operation of ultracold atomic quasi-clusters

We report several exact solutions of a two-dimensional (2D) Gross-Pitaevskii equation with an optical lattice potential, which describe the motion of an array of ultracold atomic quasi-clusters in a Bose-Einstein condensate. The velocity of the atomic quasi-clusters can be controlled by adjusting the optical potential strength so that one can stop or drive them by the optical brake. The atomic quasi-clusters form a superfluid for the propagation state or a critical insulator for the non-propagation one, and the brake and drive are associated with the quantum phase transitions between the insulator and superfluid.Received: 3 February 2003PACS: 03.75.-b Matter waves - 05.70.Jk Critical point phenomena - 05.30.Jp Boson systems - 67.90. + z Other topics in quantum fluids and solids; liquid and solid helium     

Electrical resistance of a monatomic step on a crystal surface

We have succeeded in measuring the resistance across a single atomic step through a monatomic-layer metal on a crystal surface, Si(111)(sqrt[3]xsqrt[3])-Ag, using three independent methods, which yielded consistent values of the resistance. Two of the methods were direct measurements with monolithic microscopic four-point probes and four-tip scanning tunneling microscope probes. The third method was the analysis of electron standing waves near step edges, combined with the Landauer formula for 2D conductors. The conductivity across a monatomic step was determined to be about 5 x 10(3) Omega(-1) m(-1). Electron transport across an atomic step is modeled as a tunneling process through an energy-barrier height approximately equal to the work function.     

Characterization and Thermal Behaviour of Garnets from Almandine–Pyrope Series at 1200°C

Hyperfine Interactions - The natural garnets from almandine (Fe3Al2Si3O12)–pyrope (Mg3Al2Si3O12) series with the iron to magnesium atomic ratio ranging from 0.2 to 1 were characterised and...     

从引力波探测中的压缩光到光原子钟

2020 年度“墨子量子奖”授予量子精密测量领域, 获奖科学家是 Carlton Caves, 香取秀俊和叶军. 香取秀俊和叶军又获得2021 年基础物理学突破奖. 对于引力波探测中的量子噪声,Caves 分析了海森堡不确定关系所带来的测量精度极限, 并且提出用压缩光来克服这个极限. 这个方法已经被探测引力波的激光干涉仪实际采用. 原子钟基于原子中电子改变能量状态时, 发射或吸收的电磁波, 提供了最精确的时间和频率标准. 与基于微波的原子钟相比. 光原子钟, 特别是光晶格上的大量原子, 可以达到更好的精度. 叶军的研究组将约1 万个锶原子放在3 维光晶格中, 实现光原子钟, 相对精度达到2.5 × 10-19 . 香取秀俊的研究组搭建的两个可移动光原子钟, 精度达到了5 ×10-18 , 并用来测量了引力红移, 达到地面测量的最好精度.     

珍珠明目滴眼液中微量钙的共沉淀分离原子吸收光谱分析

采用硝酸锶-碳酸钾共沉淀分离富集珍珠明目滴眼液中的微量钙,用原子吸收分光光度法测定其含量。进样溶液钙浓度在0.0～20.0μg·mL-1范围内与其422.7 nm处的吸光度成良好线性关系,检出限为0.06 μg·mL-1。该法用于珍珠明目滴眼液中钙的测定,具有灵敏、简便、快速、准确、重复性好,平均回收率为97.0%～98.3%,相对标准偏差RSD为0.4%。     

Controlling the cold collision shift in high precision atomic interferometry

We present a new method based on a transfer of population by adiabatic passage that allows one to prepare cold atomic samples with a well-defined ratio of atomic density and atom number. This method is used to perform a measurement of the cold collision frequency shift in a laser cooled cesium clock at the percent level, which makes the evaluation of the cesium fountain accuracy at the 10(-16) level realistic. With improvements, the adiabatic passage would allow measurements of density-dependent phase shifts at the 10(-3) level in high precision experiments.