导数原子光谱分析新技术研究进展

本文评介了导数测量技术在原子光谱分析中的应用研究进展。介绍了常规原子光谱信号模型及其原子光谱信号的导数模型;讨论了原子发射光谱和原子吸收光谱分析导数测量新技术原理及其分析特性。介绍了导数原子光谱技术在生物样品、环境样品、药物分析、食品饮料、金属及合金样品痕量金属元素分析中的应用。基于信号强度随时间变化的新型导数原子光谱分析新技术较常规原子光谱分析,其灵敏度和基线稳定性显著提高、检出限明显改善,在痕量和超痕量金属元素分析领域有着广阔的应用前景。     

The influence of coupling between chains on the conductivity of atomic carbon chains

This work presents a theoretical investigation on the electronic properties of double atomic carbon chains bridging graphene electrodes with density functional theory in combination with non-equilibrium Green's function. The influence of strain on the conductance of atomic carbon chains is significant. However, the coupling effect between adjacent chains dominates the intrinsic transport of double atomic carbon chains. For the coupled double atomic chains, the electron conductance of even-numbered atomic chains is significantly enhanced, while the electron conductance of odd-numbered atomic chains decreases to a certain degree, and the dependence of the conductance of double atomic chains on electrode configuration is stronger than the corresponding single atomic chain. More intriguingly, the coupled double atomic chains exhibit excellent spin-filtering properties with antiparallel spins on two electrodes. The current spin polarization stems from the coupling-induced changes of electron density and band offset reaches 100%. The coupled double atomic carbon chains have great potential application in spintronic devices and carbon-based field-effect transistors.     

双光子过程中任意初态原子的信息熵压缩

运用量子信息熵理论研究了双光子过程中任意初态二能级原子与相干场相互作用的信息熵压缩，讨论了系统初态对原子信息熵压缩的影响. 并且比较了分别从基于信息熵不确定关系和海森伯不确定关系出发得出的结果. 结果表明通过选择适当初始的原子分布角，原子的混合度和相干场的位相角，可以分别控制原子信息熵压缩的偶极矩分量数、压缩频率、压缩幅度和压缩方向. 当原子反转为零时，基于海森堡不确定关系的方差压缩定义不再有效，而信息熵压缩实现了对原子压缩效应的高灵敏量度. 关键词： 二能级原子 双光子过程 信息熵压缩 方差压缩     

原子间相互作用对V型三能级原子激光压缩性质的影响

研究了V型三能级原子玻色-爱因斯坦凝聚体与双模压缩相干态光场相互作用系统中原子激光的两个正交分量的压缩性质,并与三型三能级原子玻色-爱因斯坦凝聚体和双摸压缩相干态相互作用系中原子激光的压缩作了比较.结果表明:压缩相干态光场的初始压缩因子和凝聚体中原子间的相互作用强度对原子激光的两个正交分量的压缩有明显的影响,随光场压缩因子增大原子激光的压缩深度增加,而随原子间相互作用变强,对原子激光的正交分量的压缩的影响变浅.     

微波激射器注入原子的反转特性

建立了含克尔介质微波激射器腔场稳态光子数分布的表达式.研究了在热原子、临界和超 冷原子的方式下微波激射器中原子在稳态时的反转特性. 结果表明：注入的二能级原子在不 同方式下，原子的反转特性不一样. 在热原子方式下，原子在一部分腔长L的区域无反转， 且随原子注入速率的增大，反转区域和反转概率增大. 在临界方式下，原子的反转呈现周期 性的坍塌和复苏现象. 而在冷原子方式下，原子在腔长L的全部区域无反转. 克尔效应和失 谐量使原子的反转概率减小. 关键词： 微波激射器 原子反转 光子统计 克尔效应     

Methods for calculating the resonant part of the atomic factor in crystals with partial filling of the crystallographic position

The resonant part of the tensor atomic factor, which is important for incident radiation energies close to the atom absorption edges, is sensitive to the local environment of a scattering atom (near-range order). In this paper, a method for mathematical modeling of the resonant part of the atomic factor is developed by taking into account crystal-lattice relaxation caused by the partial filling of a crystallographic position. It is shown that an additional contribution leading to the appearance of purely resonance “forbidden” reflections can exist in the resonant atomic factor. As examples, crystals of potassium dihydrophosphate (KDP) and rubidium dihydrophosphate (RDP) are used to calculate such a contribution to the atomic factor of potassium and rubidium, and the last is compared to the thermally induced and dipole-quadrupole contributions to the atomic factor.     

莫塞莱对元素的X射线标识谱规律的发现

简述了莫塞莱生平,回顾了莫塞莱通过测量不同金属发出的X射线的波长,发现原子序数和辐射频率的关系,并指出原子序数才是原子最本质的属性.他的杰出贡献在原子物理学的发展史上产生了深刻影响。     

原子-场强度相关耦合时原子质心平移运动与内态布居的关系

基于原子与腔场共振相互作用及原子-场缀饰态,讨论了驻波腔场中两能级原子与场耦合强度相关时的原子质心的量子化平移运动对原子内态布居间的相互影响。结果表明原子平移运动敏感地依赖于原子的内态布居。特别地,当原子处于两内态等权重同位相迭加态时,平移运动呈现出很稳定的特征。     

Entropy squeezing of a moving atom and control of noise of the quantum mechanical channel via the two-photon process

Based on the quantum information theory, we have investigated the entropy squeezing of a moving two-level atom interacting with the coherent field via the quantum mechanical channel of the two-photon process. The results are compared with those of atomic squeezing based on the Heisenberg uncertainty relation. The influences of the atomic motion and field-mode structure parameter on the atomic entropy squeezing and on the control of noise of the quantum mechanical channel via the two-photon process are examined. Our results show that the squeezed period, duration of optimal entropy squeezing of a two-level atom and the noise of the quantum mechanical channel can be controlled by appropriately choosing the atomic motion and the field-mode structure parameter, respectively. The quantum mechanical channel of two-photon process is an ideal channel for quantum information (atomic quantum state) transmission. Quantum information entropy is a remarkably accurate measure of the atomic squeezing.     

原子间相互作用对原子激光压缩性质的影响

研究了原子间相互作用对光场与原子玻色-爱因斯坦凝聚体相互作用系统中耦合输出的相干原子束压缩性质的影响．结果表明：原子激光的两正交分量的涨落均可压缩，玻色-爱因斯坦凝聚体中原子间的相互作用不利于原子激光的压缩． 关键词： 玻色-爱因斯坦凝聚 压缩相干态光场 压缩原子激光     

Relaxation shift of the laser action frequency

It is found that the change of the atomic spectrum by a laser field leads to a modification of atomic relaxation. The modification of the dissipative part of the atomic kinetic equations results in a frequency shift of the laser action.     

A scheme for the generation of two-mode atomic laser

The quantum dynamic behavior of the system composed of V-type three-level atomic Bose-Einstein con-densate (BEC) interacting with two-mode coherent light field has been studied. The results show that the atoms of V-type three-level atomic BEC, which are excited to higher-level states under the action of light field, still keep their properties of coherent states. It demonstrates theoretically that two-mode atomic laser may be prepared by V-type three-level atomic BEC.     

冷原子的三维图像模拟

提出了一种用于精确模拟冷原子云的三维图像方案,这个方案比先前通过探测激光的方法所获得的二维图像更加直观和立体。该研究实现了冷原子云的模拟,捕获原子的数量约为108。原子云是几何三维形状,R_x=1.06 mm, Ry＝1.06 mm, R_z＝0.57 mm, 具有不同半轴长度的三轴椭圆体。     

Cu低维体系的结构和电子性质

基于密度泛函理论，选择generalized gradient approximation(缩写为GGA)交换作用势，使用自洽场全势的线性缀加平面波方法，计算了Cu原子组成的5种不同体系，包括面心立方晶体，两种原子面和两种原子链.结果显示，平面正六边形晶格要比正方形晶格从能量上更加稳定，原子最近邻距离稍长；而平面锯齿形原子链与直线形原子链相比也有类似的计算结果.计算还发现，锯齿形原子链中的电子态密度表现异常，能带出现间隙.另外，对比不同体系的态密度和结构，分析了量子限制和原子构型对体系电子性质的影响. 关键词： 原子链 电子结构 平面波方法 密度泛函理论     

Dynamics of a Moving Two-Level Atom Under the Influence of Intrinsic Decoherence

We present a general and fascinating problem of quantum entanglement (QE) that is calculated with the help of quantum Fisher information (QFI) and von Neumann entropy (VNE) for moving two-level atomic systems. We calculate numerically the temporal evolution of the state vector of the entire system under the influence of intrinsic decoherence for a moving two-level atom. We demonstrate that the phase shifts of an estimator parameter, intrinsic decoherence, and the atomic motion play an important and prominent role during the time evolution of the atomic system. We observe that there is a monotonic relation between the atomic quantum Fisher information (QFI) and quantum entanglement (QE) in the absence of atomic motion. We also show that at the revival time the local maximum values of QFI decreases gradually. A periodic behavior of QFI is observed in the presence of atomic motion, which becomes more important and remarkable for two-level atomic systems. Moreover, the atomic quantum Fisher information and entanglement demonstrate an opposite response during the time evolution in the presence of atomic motion. We show that the evolution of entanglement is more susceptible to the intrinsic decoherence; a considerable change occurs in the degree of entanglement when the intrinsic decoherence parameter increases. Intrinsic decoherence in the atom–field interaction represses the nonclassical effects of the atomic systems. Both the entanglement and the quantum Fisher information saturate to their lower levels for longer time scales in the presence of intrinsic decoherence. For larger values of intrinsic decoherence, the sudden death of entanglement is observed.     

Cross section of electron-nucleus bremsstrahlung near the short-wavelength limit

Using the partial-wave formalism the cross section of bremsstrahlung for a pure Coulomb field is calculated for various atomic numbers of the target nucleus and various incident electron energies. The results are compared to those of previous theories. For intermediate and large atomic numbers the latter cross sections undervalue significantly the present ones. Except for low atomic numbers the cross sections in Born approximation with the Coulomb correction by Elwert yield more accurate results than the cross sections obtained by using the approximate Sommerfeld-Maue wave function. The effect of screening is small for low atomic numbers. At nonrelativistic energies the number of required partial waves is rather large for target nuclei with high atomic numbers, contrary to the expectations. The pertinent results exceed the numerical values including screening by factors of up to five. They verify the assumption that the nonrelativistic cross section of Sommerfeld is fairly accurate even for high atomic numbers.     

双模压缩真空态与运动原子相互作用系统的场熵演化特性

利用全量子理论,研究了双模压缩真空场与运动原子相互作用系统的场熵演化特性,讨论了不同初始状态态下原子的运动速度、模场结构对场熵的影响。结果表明,场熵通过时间因子sin2(εpgt/2)度与场模结构参数,原子运动和场模结构引起了附加的“熵振荡”。     

The Entanglement Properties in the Coupled-Cavity System with the Detuning between an Atom and Cavity Field

We consider the situation that two atomic ensembles are separately trapped in coupled single-mode cavities, and each atom non-resonantly interacts with cavity field via a one-photon hopping. By employing the negativity measure of entanglement, we investigate the temporal evolution of entanglements between the cavities as well as between the cavity and atomic ensemble. By means of the numerical calculations, we discuss the influences of the number of atoms in an atomic ensemble and the detuning on the entanglement. The results show that as the number of atoms increases, the entanglement between the cavities is strengthened, contrary the entanglement between atomic ensemble and cavity is weakened. On the other hand, as the detuning increases, the entanglement between the cavities is weakened, contrary the entanglement between atomic ensemble and cavity is strengthened.

     

Evolution Properties of Atomic Fidelity in the Combined Multi-Atom-Cavity Field System

The atom fidelity is investigated in a system consisting of Mtwo-level atoms and M single-mode Gelds by use of complete quantum theory and numerical evaluation method.The influences of various system parameters on the evolution of atomic Sdelity are studied.The results show that the atomic Sdelity evolves in a Rabi oscillation manner.The oscillation frequency is mainly modulated by the coupling strength between atoms and light Geld,the atomic transition probabilities and the average photon numbers.Other factors hardly impact on the atomic fidelity.The present results may provide a useful approach to the maintenance of the atomic Sdelity in the atom cavity Seld systems.     

The effect of the counter-rotating terms on the Rabi oscillations and squeezing in the Dicke model with cavity losses

The effect of the counter-rotating terms in the Dicke model with cavity losses is examined. Numerical results for the time evolutions of the atomic population inversion, dipole moment, mean-photon number and atomic and field squeezing parameters for an initial coherent field are presented for various numbers of atoms and different cavity dampings. As a consequence of the counter-rotating terms, the appearance of new steady states for atomic population inversion and the mean-photon number is pointed out.