耦合双原子Jaynes-Cummings模型的腔场谱H

研究了处于激发态的两原子与高Q腔场相互作用单光子过程的腔场谱,给出了初始光场为光子数态、相干态、压缩真空态时的腔场谱数值计算结果,分析了原子间偶极-偶极相互作用强度gα对腔场谱结构的影响.发现真空场Rabi峰,当gα较弱时为4峰,gα较强时为3峰结构;弱场数态(n＞0)时为5峰,强场时为3峰结构.相干态和压缩真空态时,谱结构与光子数分布有关,一般为复杂的多峰结构.结果表明,gα对峰位峰高都有影响,破坏了谱结构的对称性,但这种影响只在真空场和弱场时才较明显.     

Na原子链表面等离激元特性的含时密度泛函研究

本文用含时密度泛函理论研究了线性Na原子链的表面等离激元机理.主要在原子尺度下模拟计算了体系随着原子数增加及原子间距变化的集体激发过程.研究发现线性原子链有一个普遍的特性——存在一个纵模和两个横模.两个横模一般在实验上很难被观测到.纵模随着原子链长度增加,能量红移的同时,该纵模主峰的强度呈线性增长.随着原子个数的增加,端点模式(TE)开始蓝移,能量和偶极强度都逐渐趋向饱和.横模能量被劈裂的原因概括如下:(一)每个位置的电子受到的势不同,在两端的电子受到的势要比在中间的电子受到的势要高,因此两端的电荷积累也比中间多;(二)端点存在悬挂键,所以中间的电子-电子间相互作用与端点的不一样,这两方面又都与原子间距d有关.     

Experimental progress in optical manipulation of single atoms for cavity QED

Cavity QED, as a fundamental system and research field, not only illuminates the primary aspects of decoherence and coherence in quantum dynamics, but also advances quantum information science. Manipulation of single atoms, in the context of cavity QED, is the essential element and has been becoming a hot issue for the past two decades. In this review paper, we will concentrate on the experimental aspects for manipulating the neutral atoms strongly coupled to a high-finesse cavity in the optical regime, including atomic cooling and trapping, different configurations of atom transportation and the wide variety of quantum outgrowths based on cavity QED, such as one atom laser, single photon source, etc. The cavity QED system at Shanxi University is briefly introduced.      

Line shape analysis of two-colour photoassociation spectra on the example of the Cs ground state

Two-photon photoassociation spectra in a Λ-type excitation scheme are analysed under the systematically varied experimental conditions of frequency detunings and laser intensities. Line shape fits are presented as well as the investigation of intensity and detuning dependent line shifts. From both we determine the attained spectroscopic precision, that is corrected for a systematic line shift due to the thermal distribution of atoms in the trap. An energy correction for this effect is given. Information about the feasibility of generating translationally cold molecules in a well defined rotational and vibrational level by the photoassociation process is derived from the analysis. Received 21 May 2002 Published online 15 October 2002 RID="a" ID="a"Current address e-mail: christian.lisdat@ptb.de RID="b" ID="b"e-mail: pierre.pillet@lac.u-psud.fr     

STUDY ON THE SEQUENCE STRUCTURE OF SBR BY 13C—NMR METHOD Ⅰ. ASSIGNMENT FOR UNSATURAT CARBONS SPECTRA*

The sequence structures of emulsion-processed SBR and solution-processed (by lithium catalyst) SBR were investigated by ~(13)C-NMR spectroscopy. Seventeen peaks within unsaturated carbon region were recorded under the adopted experimental conditions. Assignments for these peaks were made by empirical-parameter-evaluation method.     

Diboron Bonds Between BX3 (X=H,F, CH3) and BYZ2 (Y=H,F; Z=CO,N2, CNH)

The ability of B atoms on two different molecules to engage with one another in a noncovalent diboron bond is studied by ab initio calculations. Due to electron donation from its substituents, the trivalent B atom of BYZ₂ (Z=CO, N₂, and CNH; Y=H and F) has the ability to in turn donate charge to the B of a BX₃ molecule (X=H, F, and CH₃), thus forming a B⋅⋅⋅B diboron bond. These bonds are of two different strengths and character. BH(CO)₂ and BH(CNH)₂, and their fluorosubstituted analogues BF(CO)₂ and BF(CNH)₂, engage in a typical noncovalent bond with B(CH₃)₃ and BF₃, with interaction energies in the 3–8 kcal/mol range. Certain other combinations result in a much stronger diboron bond, in the 26–44 kcal/mol range, and with a high degree of covalent character. Bonds of this type occur when BH₃ is added to BH(CO)₂, BH(CNH)₂, BH(N₂)₂, and BF(CO)₂, or in the complexes of BH(N₂)₂ with B(CH₃)₃ and BF₃. The weaker noncovalent bonds are held together by roughly equal electrostatic and dispersion components, complemented by smaller polarization energy, while polarization is primarily responsible for the stronger ones.     

Synthesis, Crystal Structure and Electrochemical Properties of One-dimensional Chain Coordination Polymer [Co(Ⅱ)(C6H5CH=CHCOOH)2(4,4''-bipy)(H2O)5]n

A one-dimensional chain coordination polymer [Co(Ⅱ)(C6H5CH=CHCOOH)2(4,4'-bipy)(H2O)5]n has been synthesized with cinnamylic acid, 4,4'-bipy and cobaltous chloride as raw materials. Crystal data for this complex: monoclinic, space group P21/c, a - 1.1481(3), b =1.1230(2), c = 1.1759(3) nm, β = 97.054(4)°, V = 1.5046(6) nm3, Mr= 617.50, Dc = 1.363 g/cm3, Z= 2, μ(MoKα) = 0.627 mm-1, F(000) = 646, S = 1.062, R 0.0443 and wR = 0.1178. The crystal structure shows that two neighboring cobalt(Ⅱ) ions are linked together by one 4,4'-bipy, and the whole complex molecule adopts a one-dimensional chain structure. Each cobalt(Ⅱ) ion is coordinated with two nitrogen atoms from two 4,4'-bipy molecules and four oxygen atoms from four water molecules, giving a distorted octahedral coordination geometry. The electrochemical properties were analyzed by combining with the crystal structure.     

Partitioning behaviour of organic compounds between ionic liquids and supercritical fluids

Applications and prospects of two-phase, tuneable solvent systems composed of ionic liquids (ILs) and supercritical fluids with an emphasis on supercritical carbon dioxide (scCO(2)) are reviewed. The IL-scCO(2) biphasic systems have increasingly been used in diverse fields of chemistry and technology, and some examples of these applications are mentioned here. Rational design of such applications can obviously benefit from pertinent data on phase equilibria including the partition coefficients of the prospective products and reactants between the two phases. Therefore, a reliable technique to measure the limiting partition coefficients would be of value. Here, the pros and cons of supercritical fluid chromatography in this respect are discussed. An overview of methods for predictive thermodynamic modelling of binary (IL-scCO(2)) and ternary (solute-IL-scCO(2)) systems is also included.     

铅原子非共振多光子电离过程的研究

在激光波长为1064nm、532nm和355nm下,研究了铅原子的非共振多光子过程.通过改变激光脉冲的线宽研究了铅原子非共振7-光子电离速率和激光统计性的依赖关系.