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	1. Design and Simulation of a Trap-based Pulsed Slow Positron Beam
	He Chunqing,Wang Juncheng,Zhu Jun,Wang Shaojie
	Physics 30 October 2012
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	Abstract:A simple pulsed slow positron beam based on a Penning-trap has been designed and is being constructed in Wuhan University. The cooled positrons from the trap with very low energy dispersion are dumped and chopped to pulses of a few tens of ns in width. Positron pulses are bunched by adjusting the potential of drift tube using an arbitrary wave generator, then accelerated to the target. Influences of the pulse width, the energy dispersion of positrons etc. on the time resolution of bunched positron pulse are simulated. The result shows that lower energy dispersion of positrons leads to much narrower positron pulses, indicating that a trap-based slow positron beam has a great advantage in developing a pulsed slow positron beam.
	TO cite this article:He Chunqing,Wang Juncheng,Zhu Jun, et al. Design and Simulation of a Trap-based Pulsed Slow Positron Beam[OL].[30 October 2012] http://en.paper.edu.cn/en_releasepaper/content/4493655


	2. Cold cesium molecules produced directly in a magneto optical trap
	ZHANG Hongshan,ZHAO Yanting,JI Zhonghua
	Physics 01 March 2012
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	Abstract:We report on the observation of ultracold ground electric-state cesium molecules produced directly in a magneto-optical trap with a good signal-to-noise ratio. These molecules arise from the photoassociation of magneto-optical trap lasers and they are detected by resonantly enhanced multiphoton ionization technology. The production rate of ultracold cesium molecules is up to 4×104 s-1. We measure the characteristic time of the ground electric-state cesium molecules generated in the experiment and investigate the Cs2+ molecular ion intensity as a function of the trapping laser intensity and the ionization pulse laser energy. We conclude that the production of cold cesium molecules may be enhanced by using appropriate experimental parameters, which is useful for future experiments involving the production and trapping of ultracold ground electric-state molecules.
	TO cite this article:ZHANG Hongshan,ZHAO Yanting,JI Zhonghua. Cold cesium molecules produced directly in a magneto optical trap[OL].[ 1 March 2012] http://en.paper.edu.cn/en_releasepaper/content/4468997

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	3. Investigation of cold collision in a Rb-Cs magneto-optical trap
	JI Zhonghua,ZHAO Yanting
	Physics 01 March 2012
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	Abstract:We have measured the interspecies trap loss rate coefficient. The experiment was measured the rubidium atom trap loss rate coefficient as a function of Rb trapping laser intensity by loading process for rubidium atom in either presence or absence of cesium atomic cloud. The trap loss rate coefficient decreases as the Rb trapping laser intensity increases where the trap loss caused by hyperfine-state changing collision is suppressed due to the increasing Rb trap depth. The corresponding Rb trapping laser intensities are 7.8 mW/cm2, 12.1 mW/cm2 and 34.7 mW/cm2 respectively. The experimental results agree with the calculated critical intensity IC of Rb trapping laser by a simple Doppler model.
	TO cite this article:JI Zhonghua,ZHAO Yanting. Investigation of cold collision in a Rb-Cs magneto-optical trap[OL].[ 1 March 2012] http://en.paper.edu.cn/en_releasepaper/content/4469074


	4. Pressure-induced structural transition and thermodynamic properties of RhN2 and effect of metallic bonding
	Kuang XiaoYu,Liu Jun,Mao Aijie
	Physics 15 December 2011
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	Abstract:Using first-principles calculations, the elastic constant, structural phase transition and effect of metallic bonding on the hardness of RhN2 under high pressure are investigated by means of the pseudopotential plane-waves method. Three structures are chosen to investigate for RhN2, namely, simple hexagonal P6/mmm (SH), orthorhombic Pnnm (marcasite) and simple tetragonal P4/mbm (ST). Our calculations show that the SH phase is energetically more stable than the other two phases at zero pressure. On the basis of the third-order Birch-Murnaghan equation of states, we find that phase transition pressure from SH to marcasite structure and marcasite to ST structure are 1.09 GPa and 354.57 GPa, respectively. Elastic constants, formation enthalpies, shear modulus, Young's modulus and Debye temperature of RhN2 are derived. The calculated values are generally speaking in good agreement with the previous theoretical results. Meanwhile, it is found that the pressure has an important influence on physical properties. Moreover, the effect of metallic bonding on the hardness of RhN2 is investigated. This is a quantitative investigation on the structural properties of RhN2, and it still awaits experimental confirmation.
	TO cite this article:Kuang XiaoYu,Liu Jun,Mao Aijie. Pressure-induced structural transition and thermodynamic properties of RhN2 and effect of metallic bonding[OL].[15 December 2011] http://en.paper.edu.cn/en_releasepaper/content/4454972


	5. A comparative study on the geometries, stabilities and electronic properties between bimetallic AgnX (X=Au, Cu; n=1-8) and pure silver clusters
	Kuang Xiaoyu,Ding LiPing,Mao Aijie
	Physics 15 December 2011
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	Abstract:Using the meta-generalized gradient approximation (meta-GGA) exchange correlation TPSS functional, the geometric structures, relative stabilities and electronic properties of bimetallic AgnX (X=Au, Cu; n=1-8) clusters are systematically investigated and compare them with those of pure silver clusters. The optimized structures show that the transition point from preferentially planar to three-dimensional structure occurs at n=6 for the AgnAu clusters, while n=5 for AgnCu clusters. For different-sized AgnX clusters, one X (X=Au or Cu) atom substituted Agn+1 structures is a dominant growth pattern. The calculated fragmentation energies, second-order differences in energies, and the highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps show interesting odd-even oscillation behaviors, indicating that Ag2, 4, 6, 8 and Ag1, 3, 5, 7X (X=Au, Cu) clusters keep higher stability in comparison with their neighboring clusters. The natural population analysis reveals that the charges transfer from the Agn host to the impurity atom except for Ag2Cu cluster. Moreover, vertical ionization potential (VIP), vertical electronic affinity (VEA) and chemical hardness (η) are in depth discussed and compared. The same odd-even oscillations are found for the VIP and of the AgnX (X=Au, Cu; n=1-8) clusters.
	TO cite this article:Kuang Xiaoyu,Ding LiPing,Mao Aijie. A comparative study on the geometries, stabilities and electronic properties between bimetallic AgnX (X=Au, Cu; n=1-8) and pure silver clusters[OL].[15 December 2011] http://en.paper.edu.cn/en_releasepaper/content/4454299


	6. Observation of intermolecular double-quantum coherence signal dips in nuclear magnetic resonance
	Shen Guiping,Cai Congbo,Cai Shuhui,Chen Zhong
	Physics 05 April 2011
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	Abstract:The correlated spectroscopy revamped with asymmetric Z-gradient echo detection sequence was modified to investigate intermolecular double-quantum coherence nuclear magnetic resonance signal dips in highly polarized spin systems. It is found that the occurrence of intermolecular double-quantum coherence signal dips is related to the sample geometry, field inhomogeneity and dipolar correlation distance. If the field inhomogeneity is refocused, the signal dip occurs at a fixed position whenever the dipolar correlation distance approaches the sample dimension. However, the position is shifted when field inhomogeneity exists. Experiments and simulations were performed to validate our theoretic analysis. These signal features may offer a unique way to investigate porous structures and may find applications in biomedicine and materials science.
	TO cite this article:Shen Guiping,Cai Congbo,Cai Shuhui, et al. Observation of intermolecular double-quantum coherence signal dips in nuclear magnetic resonance[OL].[ 5 April 2011] http://en.paper.edu.cn/en_releasepaper/content/4420309


	7. Detection and characterization of intermolecular multiple-quantum coherence NMR signal of IS (I=1/2, S=3/2) spin systems
	Zhang Wen,Chen Song,Cai Shuhui,Chen Zhong
	Physics 15 December 2010
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	Abstract:Intermolecular multiple-quantum coherences (iMQCs) have some intrinsic properties different from conventional single-quantum coherences in solution NMR. In this paper, we extended our study to heteronuclear iMQCs in IS (I=1/2, S=3/2) spin systems. A sample of sodium chloride (NaCl) water solution was taken as an example. Heteronuclear multiple-quantum Correlated Revamped by Asymmetric Z-gradient Echo Detection (CRAZED) experiments were performed. One- and two-dimensional heteronuclear iMQC spectra were obtained. The quantum-mechanical treatment was used to deduce the signal expressions. Magical angle experiments validate that the signals are indeed from intermolecular dipolar interaction and insensitive to the imperfection of radio-frequency (RF) flip angles. Both experimental results and theoretical analysis indicate that heteronuclear CRAZED experiment allows coherence transfer from spin-3/2 nuclei to spin-1/2, and vice verse. Furthermore, the dependences of iMQC signal intensities on RF pulse flip angles follow the same rules as those for heteronuclear IS (I=1/2, S=1/2 or 1) spin systems.
	TO cite this article:Zhang Wen,Chen Song,Cai Shuhui, et al. Detection and characterization of intermolecular multiple-quantum coherence NMR signal of IS (I=1/2, S=3/2) spin systems[OL].[15 December 2010] http://en.paper.edu.cn/en_releasepaper/content/4398006


	8. Potential Sputtering of Highly Charged Ions on Copper and Tungsten Surfaces
	Wang Tieshan,Ding Jingjie,Cheng Rui,Lu Xia,Zhao Yongtao
	Physics 05 December 2010
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	Abstract:The sputtering yields for copper (Cu) and tungsten (W) targets bombarded by Arq+ (1≤q≤16) and Pbq+ (4≤q≤36) ions were measured. The threshold effect was found for the potential sputtering on metals in this work. The sputtering yields remain constant when q<24, however, they grow dramatically with the charge state q when q≥24. For comparison, the sputtering yields on insulator (SiO2) and semiconductor (Si) were also studied. It increases almost linearly with q in Pbq+ impact case. It is considered that the potential sputtering is strongly dependent on the target material properties, especially the conductivity.
	TO cite this article:Wang Tieshan,Ding Jingjie,Cheng Rui, et al. Potential Sputtering of Highly Charged Ions on Copper and Tungsten Surfaces[OL].[ 5 December 2010] http://en.paper.edu.cn/en_releasepaper/content/4395166


	9. Structures and absorption optical spectra of silicon cluster Si9 via first-principles calculations
	Li Zhe,Chen Xiangrong,Lan Junqing,Bai Yulin
	Physics 23 December 2009
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	Abstract:Using a finite-difference pseudopotential density-functional theory in real space and Langevin molecular dynamics annealing technique, we perform calculations to determine the ground-state structure of the silicon cluster Si9. It is found that the ground-state structure of Si9 cluster is a distorted capped hexahedron shape with Cs symmetry. And then, we implement the linear response theory within the time-dependent local density-functional formalism (TDLDA) to calculate the corresponding optical absorption spectra. The spectral feature may help to identify isomers and can be used for comparison against future experimental investigations.
	TO cite this article:Li Zhe,Chen Xiangrong,Lan Junqing, et al. Structures and absorption optical spectra of silicon cluster Si9 via first-principles calculations[J].


	10. A meaningful modification for the Tang-Toennies potential model: Application to He-He potential
	X.W. Sheng,P.Li
	Physics 24 August 2009
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	Abstract:the repulsive wall of the Tang-Toennies model is, unfortunately, generally too stiff. In addition, the repulsive potential represented by a Born-Mayer term in the Tang-Toennies potential does not allow any physical insight into the nature of intermolecular interactions. In this work a modification of the Tang-Toennies potential model is presented. The repulsive part of the Tang-Toennies model is replaced by the . This term is essentially from Duman and Smirnov who assume the exchange of only one pair of electrons at any one time. After this modification, all of the terms in the modified Tang-Toennies model has a definitely physical meaning. For the He dimer, this new modified Tang-Toennies potential model well coincide with the original Tang-Toennies model in the van der Waals range ( R > 5 a.u. ). In addition this new modified potential model is in excellent agreement with the latest experimental and theoretical results in the repulsive wall ( R > 2 a.u. ). The same method can be applied to other homonuclear systems.
	TO cite this article:X.W. Sheng,P.Li. A meaningful modification for the Tang-Toennies potential model: Application to He-He potential[OL].[24 August 2009] http://en.paper.edu.cn/en_releasepaper/content/34608

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