|
Strong Outcoupling from Spin-2 87Rb Bose--Einstein Condensates
YANG Fan, XIA Lin, ZHOU Xiao-Ji, MA Xiu-Quan, CHEN Xu-Zong
Chin. Phys. Lett. 2005, 22 (7):
1596-1599
.
A pulsed atom laser is experimentally demonstrated by means of outcoupling coherent atoms from 87Rb Bose--Einstein condensates in magnetic trap via radio-frequency pulses. To study the strong outcoupling dynamics of the atom laser, the original |F=2,mF=2> condensate and the coupled |F=2,mF=1> component, both of which overlap in space usually, are separated spatially by collective oscillations. The number of atoms in three of the five Zeeman states are measured and compared with the theoretical results.
|
|
Dynamical Equations for Quantum Information and Application in Information Channel
BI Qiao, XING Xiu-San, H. E. Ruda
Chin. Phys. Lett. 2005, 22 (7):
1618-1621
.
We establish several dynamical equations for quantum information density. It is demonstrated that quantum information density shares the same formalism of the Liouville equation, subdynamics kinetic equation and Fokker--Planck equation as the density operator and also possesses the superposition property. These allow one to use quantum information density directly to model quantum information. The kinetic equations for quantum information density reveal that the dynamical process of quantum information may be related to dissipative, Markovian, or diffusional information flows, together causing irreversibility. Finally, we discuss superposition of quantum information density, which allows us to construct a quantum information channel in the coherent state representation using harmonic oscillator based encoded quantum information, and obtain a formula for quantum dynamical mutual information.
|
|
Isobaric Identification Using Gas-Filled Time-of-Flight Measurements in an Accelerator Mass Spectrometry
GUAN Yong-Jing, RUAN Xiang-Dong, HE Ming, WANG Hui-Juan, LI Guo-Qiang, WU Shao-Yong, DONG Ke-Jun, LIN Min, JIANG Shan
Chin. Phys. Lett. 2005, 22 (7):
1622-1624
.
A gas-filled time-of-flight (GF-TOF) detector has been built and developed to improve the ability of isobaric identification in accelerator mass spectrometry (AMS) measurements, and a time resolution (without gas filled) of better than 350ps is achieved. The GF-TOF detector is tested by means of measuring a standard AgCl (36Cl/Cl =7.6×10-9g/g) sample with the 36Cl ion energy of 64, 49 and 33MeV, respectively. 36Cl and 36S particles were successfully separated in the TOF spectra output from the GF-TOF detector. The comparison between the gas-filled time-of-flight method and the ΔE-E method is described. Some results relative to the GF-TOF method are given as well.
|
|
Super-Resolution Imaging on Microfluidic Super-Resolution Near-Field Structure
WANG Pei, TANG Lin, ZHANG Dou-Guo, LU Yong-Hua, JIAO Xiao-Jin, XIE Jian-Ping, MING Hai
Chin. Phys. Lett. 2005, 22 (7):
1625-1627
.
We present a new concept of the microfluidic super-resolution near-field structure (MSRENS) based on a microfluidic structure and a super-resolution near-field structure. The near-field distance control, "nano-probe" and scanning can be realized simultaneously using the MSRENS, which is similar to a near-field scanning optical microscope. The design and simulation results are presented. Numerical simulation has demonstrated that the MSRENS with spatial resolution beyond the diffraction limit could be applicable in chemistry, biologics, and many other fields.
|
|
Measurements of g-Factor of Rotational Levels in 83Y
YUAN Da-Qing, ZHENG Yong-Nan, ZHOU Dong-Mei, ZUO Yi, DU En-Peng, DUAN Xiao, WANG Chao-Hui, LUO Qi, WU Xiao-Guang, LI Guang-Sheng, WEN Shu-Xian, XU Guo-Ji, GAO Zao-Chun, CHEN Yong-Shou, ZHU Sheng-Yun
Chin. Phys. Lett. 2005, 22 (7):
1628-1630
.
The g-factors of the positive parity rotational levels up to spin I=41/2+ in 83Y have been measured by a transient-magnetic-field ion implantation perturbed angular distribution method. The experimentally measured g-factors show the g9/2 proton alignment followed by the g9/2 neutron alignment. The measured g-factors are in good agreement with the results calculated by an empirical formula based on the cranking shell model.
|
|
Electron Momentum Distributions of the Highest Occupied Molecular Orbital of CF3Br: Delocalization of Halogen Lone-Pair Orbitals
WU Xing-Ju, CHEN Xiang-Jun, CHEN Li-Qing, LI Zhong-Jun, YANG Xue-Feng, SHAN Xu, ZHENG Yan-You, XU Ke-Zun
Chin. Phys. Lett. 2005, 22 (7):
1649-1651
.
The highest occupied molecular orbital (HOMO) of trifluorobromomethane (CF3Br) is studied by binary (e, 2e) electron momentum spectroscopy. The experimental momentum profile of the HOMO is compared with the Hartree-Fock (HF) and density functional theory (DFT-B3LYP) calculations. The calculated results largely depend on the size of basis sets rather than theoretical methods. Both the HF and DFT calculations using the 6-311++G** basis set give a good explanation to the experiment. Delocalization of halogen lone-pair orbitals in the series molecules CF3X (X= F, Cl, Br) has been investigated.
|
|
Experimental Study of Effect of Medium Boundary on Light Distribution in Tissue Phantoms
XU Tang, ZHANG Chun-Ping, TIAN Jian-Guo, SONG Feng, WANG Xin-Yu, ZHAO Cheng-Mei
Chin. Phys. Lett. 2005, 22 (7):
1660-1663
.
An experimental method for investigating the effect of medium boundary on distributions of light in the biological tissue phantom intralipid is presented. Measurements of distributions of light in intralipid-10% suspensions at 633nm are described, in which a narrow collimated beam is incident on the surface of the phantoms and into the different depths inside of the phantoms. The experimental results show that the effect of the boundary of the medium on the curves geometry of light distributions is trivial, but the effect on intensity of scattering light is obvious, the maximal relative change of the energy fluence reaches 53.8 % and the position of the peak of the energy fluence curve has a shift of 1.1mm in the reverse direction of incident light for the phantom with albedo a = 0.998, and the effect of the boundary is decreased with the increase of the absorption coefficients of tissue phantoms. The experimental results were analysed by the diffusion theory. These studies will be helpful for further understandings of the relation between the boundary of biological tissue and the distribution of light in tissue.
|
|
High-Average-Power Nanosecond Quasi-Phase-Matched Single-Pass Optical Parametric Generator in Periodically Poled Lithium Niobate
ZHANG Bai-Gang, , YAO Jian-Quan, , LU Yang, XU De-Gang, JI Feng, ZHANG Tie-Li, ZHAO Xin, WANG Peng, , XU Ke-Xin
Chin. Phys. Lett. 2005, 22 (7):
1691-1693
.
A pulsed nanosecond optical parametric generator (OPG) in periodically poled lithium niobate (PPLN) crystal is presented. The pump laser is an acousto-optically Q-switched Nd:YVO4 laser with the maximum average power of 6.58W. When the repetition rate is 50kHz and the pulse width of the pump source is 80ns, the maximum average total output power of the single-pass PPLN OPG is about 1.9W, which includes 1.322W of 1.536μm signal radiation. The length of the PPLN crystal is only 38.7mm (at room temperature) with a grating period of 28.93μm (at room temperature). The 1.502--1.536μm signal radiation and 3.652--3.465μm idler radiation are obtained by adjusting the PPLN crystal temperature from 155°C to 250°C.
|
|
Thomson Scattering Process in Laser-Produced Plasmas
YU Quan-Zhi, ZHANG Jie, LI Yu-Tong, ZHENG Jun, YAN Fei, LU Xin, WANG Zhe-Bin, ZHENG Jian, YU Chang-Xuan, JIANG Xiao-Hua, LI Wen-Hong, LIU Shen-Ye, ZHENG Zhi-Jian
Chin. Phys. Lett. 2005, 22 (7):
1717-1720
.
We present the evolutions of the electron temperature and plasma expansion velocity with Thomson scattering experiment. The observed time-resolved ion-acoustic image is reproduced by a numerical code which couples the Thomson scattering theory with the output parameters of the one-dimensional hydrocode MEDUSA.
|
|
Effects of Confined Laser Ablation on Laser Plasma Propulsion
ZHENG Zhi-Yuan, ZHANG Jie, LU Xin, HAO Zuo-Qiang, Xu Miao-Hua, WANG Zhao-Hua, WEI Zhi-Yi
Chin. Phys. Lett. 2005, 22 (7):
1725-1728
.
We investigate the effects of confined laser ablation on laser plasma propulsion. Compared with planar ablation, the cavity ablation provides an effective way to obtain a large target momentum and a high coupling coefficient. When laser pulses are focused into a cavity with 1mm diameter and 2mm depth, a high coupling coefficient is obtained. By using a glass layer to cover the cavity, the coupling coefficient is enhanced by 10 times. Meanwhile, it is found that with the increase of the target surface size, the target momentum presents a linear increase.
|
|
Electron Holography of Barrier Structures in Co/ZrAlOx/Co Magnetic Tunnel Junctions
ZHANG Zhe, ZHU Tao, SHEN Feng, SHENG Wen-Ting, WANG Wei-Gang, XIAO John Q, ZHANG Ze,
Chin. Phys. Lett. 2005, 22 (7):
1732-1735
.
We investigate the potential profiles and elemental distribution of barriers in Co/ZrAlOx/Co magnetic tunnel junctions (MTJs) using electron holography (EH) and scanning transmission electron microscopy. The MTJ barriers are introduced by oxidizing a bilayer consisting with a uniform 0.45-nm Al layer and a wedge-shaped Zr layer (0-2nm). From the scanning transmission electron microscopy, AlOx and ZrOx layers are mixed together, indicating that compact AlOx layer cannot be formed in such a bilayer structure of barriers. The EH results reveal that there are no sharp interfaces between the barrier and magnetic electrodes, which may be responsible for a smaller tunnelling magnetoresistance compared with the MTJs of Co/AlOx/Co.
|
|
Glass-Forming Ability of an Iron-Based Alloy Enhanced by Co Addition and Evaluated by a New Criterion
CHEN Qing-Jun, SHEN Jun, FAN Hong-Bo, SUN Jian-Fei, HUANG Yong-Jiang, MCCARTNEY D. G.
Chin. Phys. Lett. 2005, 22 (7):
1736-1738
.
A new Fe-based alloy that can be cast into a fully amorphous rod with a diameter of at least 16mm by the conventional copper-mould casting technique is obtained by partially replacing Fe with Co in a previously reported Fe-based bulk metallic glass. The preliminary thermodynamic analysis indicates that the Co-containing alloy has a significantly lower Gibbs free energy difference between the undercooled melt and the corresponding crystalline solid, compared to the Co-free alloy, reflecting the dramatic role of the Co addition in stabilizing the supercooled melt and facilitating glass formation in iron-based alloys. Here, a new criterion, derived from the classical nucleation and growth theory, is introduced to evaluate the glass-forming ability of Fe-based bulk metallic glasses.
|
|
Sound Velocity and Release Behaviour of Shock-Compressed LY12 Al
YU Yu-Ying, TAN Hua, DAI Cheng-Da, HU Jian-Bo, CHEN Da-Nian
Chin. Phys. Lett. 2005, 22 (7):
1742-1745
.
A velocity interferometer system for any reflector (VISAR) is used to measure the sound velocity of LY12 Al shock-compressed to peak pressures of 20, 32, 55 and 71GPa. Unloading wave velocities from these pressures are obtained from the observed particle velocity profiles at the LY12 Al/LiF window interface; and the longitudinal, bulk and shear sound velocities at the initial Hugoniot state are well determined. The histories of stress, strain, density or volume, and particle velocity along the release paths are calculated by the impedance-matching method based on the unloading sound velocity data. It is revealed that the release behaviour of shocked LY12 Al departures obviously from the elastic perfectly-plastic response.
|
|
Simulation of Anisotropic Resistivity for Mixed-Phase Manganite La2/3Ca1/3MnO3 Thin Films
ZHOU Qing-Li, GUAN Dong-Yi, JIN Kui-Juan, ZHAO Kun, CHEN Zheng-Hao, LU Hui-Bin, ZHOU Yue-Liang, HAN Peng, YANG Guo-Zhen
Chin. Phys. Lett. 2005, 22 (7):
1749-1752
.
We utilize the random network model based on phase separation scenario to simulate the conductive behaviour and anisotropic characteristics of resistivity for La2/3Ca1/3MnO3 (LCMO) thin films. The simulated results agree well with our experimental data, showing a metal-to-insulator transition from a high-T paramagnetic (PM) insulating phase to a low-T ferromagnetic (FM) metallic phase in both the untilted film deposited on a (001) SrTiO3 (STO) substrate and the tilted film grown on a vicinal cut STO substrate. It is found that the resistivity of the tilted sample is higher than that of the untilted one, displaying prominent anisotropic characteristics. The studies reveal that the tilting not only decreases the conduction of the FM domains, but also increases the activation energy of the PM regions, inducing the enhancement of resistivity. All those results suggest that the intrinsic inhomogeneity in the phase separation system plays a significant role in the electrical conductivity and the resistive anisotropy is related to the structure of the crystal lattice.
|
|
Fabrication and Magnetic Properties of Co-Doped TiO2 Powders Studied by Nuclear Magnetic Resonance
GE Shi-Hui, WANG Xin-Wei, KOU Xiao-Ming, ZHOU Xue-Yun, XI Li, ZUO Ya-Lu, YANG Xiao-Lin, ZHAO Yu-Xuan
Chin. Phys. Lett. 2005, 22 (7):
1772-1775
.
Co0.04Ti0.96O2 powders are fabricated by sol-gel method. The structure and magnetic properties are investigated under different annealing conditions systematically with emphasis on the influence of oxygen pressure. Pure anatase structure was acquired for all the samples annealed at 450°C for one hour. The samples annealed in air exhibit evident room-temperature ferromagnetism (RTFM) with a small magnetic moment of 0.029μB per Co atom and coercivity Hc of 26Oe, while the samples annealed in vacuum have strong RTFM with a larger magnetic moment of 1.18μB per Co atom and Hc of 430Oe. The zero-field spin echo nuclear magnetic resonance spectrum of 59Co is obtained to prove the existence of Co clusters in the latter samples, implying that the Co clusters are responsible for the strong RTFM in the samples annealed in vacuum. No Co cluster could be observed using both XPS and NMR techniques in the samples annealed in air, implying that the RTFM found in these samples is intrinsic.
|
|
Magnetic and Crystalline Microstructures of Fe--Pt--B Nanocomposite Ribbons
FANG Yi-Kun, CHANG Cheng-Wu, CHANG Wen-Cheng, XIA Ai-Lin, CHEN Qiang, GE Hong-Liang, HAN Bao-Shan
Chin. Phys. Lett. 2005, 22 (7):
1776-1779
.
We investigate magnetic and crystalline microstructures of melt-spun (Fe0.675Pt0.325)100-xBx (x=12, 14, 16, 18, 20) nanocomposite ribbons after optimal thermal treatment using a magnetic force microscope. The magnetic microstructures are characterized by darker spots adjacent to brighter ones in a sub-micro scale and in random distribution. It is found that the strength of the exchange coupling interaction between the crystals in the 10-100nm scale, implied by the maximum value (δM)max of the Henkel plot, could be roughly described by the ratio of the average width of the magnetic spots w to the average crystal size for the ribbons. Moreover, we find that the intrinsic coercivity jHc of the ribbons is sensitive to their crystal sizes, and the smaller D, the higher jHc. Finally, by using roughness analysis, the curve of the root mean square values (δФ)rms of the phase shift of the magnetic force images versus the boron content x is obtained, which is qualitatively consistent with that of the magnetization σ12kOe of the ribbons versus x.
|
|
Electron Spin Resonance Studies of Mn2+ in Freshwater Snail Shells: Pomacea Canaliculata Lamarck and Fossilized Snail Shell
N. Udomkan, S. Meejoo, P. Limsuwan, P. Winotai, Y. Chaimanee
Chin. Phys. Lett. 2005, 22 (7):
1780-1783
.
We study paramagnetic Mn2+ ions present in the nowadays shells of univalve freshwater snails of Pomacea canaliculata lamarck (PCL) and the fossilized freshwater snail (FFS), Viviparus. All these shells are abundant in Thailand. The PCL shells were ground into fine powder. A set of seven samples were then separately annealed for 2h in air atmosphere at different annealing temperatures while the FFS powder was characterized as-received. The PCL shells mainly consist of aragonite and a fraction of calcite. The heat treatments of the PCL powder samples at temperature higher than 450°C resulted in an irreversible phase transformation from aragonite to calcite. However, it is found that the FFS shell is mainly made of calcite, with a minor fraction of aragonite. The crystal structure of the high-temperature-annealed PCL samples are quite similar to that of FFS, which indicates that the metamorphosis (aragonite → calcite) in the FFS shell had occurred but was not yet completed, although it had remained under the pressure and temperature of the Earth’s crusts over millions of years. Our detailed ESR spectral analyses of PCL and FFS show that Mn2+ ions enter the Ca2+ sites during a biomineralization process. Simulated ESR parameters of PCL-500 of Mn2+ at a uniaxial site of calcite are reported. It is surprising to find that the ratio of Mn2+ concentration present in FFS to those in PCL shells evaluated from ESR spectra is as much as 10:1.
|
|
Effect of Microstructure of TiO2 Thin Films on Optical Band Gap Energy
TIAN Guang-Lei, HE Hong-Bo, SHAO Jian-Da
Chin. Phys. Lett. 2005, 22 (7):
1787-1789
.
TiO2 coatings are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for four hours, the spectra and XRD patterns of TiO2 thin film are obtained. XRD patterns reveal that only anatase phase can be observed in TiO2 coatings regardless of the different annealing temperatures, and with the increasing annealing temperature, the grain size gradually increases. The relationship between the energy gap and microstructure of anatase is determined and discussed. The quantum confinement effect is observed that with the increasing grain size of TiO2 thin film, the band gap energy shifts from 3.4eV to 3.21eV. Moreover, other possible influence of the TiO2 thin-film microstructure, such as surface roughness and thin film absorption, on band gap energy is also expected.
|
|
Highly Efficient Electrophosphorescence from a Grafted Biscyclometalated Iridium Complex with Triarylamine Unit in Polymer Light-Emitting Devices
ZHU Mei-Xiang, WU Zhong-Lian, JIANG Chang-Yun, LIU Jian, LI Jian-Ren, XING Kong-Qiang, YANG Yu-Ping, GAN Quan,
CAO Yong, ZHU Wei-Guo
Chin. Phys. Lett. 2005, 22 (7):
1793-1796
.
The electroluminescence performance from a novel grafted cyclometalated iridium complex (BuPhNPPy)$_{2}$Ir(acac) with triarylmine unit, where BuPhNPPy is N,N-di(4-tert-butylphenyl)-4-(2-pyridyl) phenylamine and Hacac is acetylacetone, is demonstrated in the double-layered polymer light-emitting devices (PLEDs). The PLEDs emit intense green phosphorescence at 533nm with a shoulder peak of 566nm employing 4wt.% (BuPhNPPy)2Ir(acac) doped a blend of poly(vinylcarbazole) (PVK) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) as the emitting layer. A maximum luminance of 14610cd/m2 at voltage of 24V and a maximum external quantum efficiency Eext of 10.4% photons per electron (ph/el) at current density of 32mA/cm2 are achieved. When the current density is raised to 100mA/cm2, Eext of the device still remained to 8.3% ph/el. This indicates that the triplet--triplet annihilation is restrained more effectively at high current density. The improvement of electrophosphorescence performances of the iridium complex may be contributed to an ortho-substituent effect of grafted triarylmine unit.
|
|
White Organic Light-Emitting Devices Based on 2-(2-Hydroxyphenyl) Benzothiazole and Its Chelate Metal Complex
WU Xiao-Ming, HUA Yu-Lin, WANG Zhao-Qi, ZHENG Jia-Jin, FENG Xiu-Lan, SUN Yuan-Yuan
Chin. Phys. Lett. 2005, 22 (7):
1797-1799
.
We present three kinds of organic light-emitting devices (OLED) fabricated to achieve the emission of bright and pure white light. Device A, with a double-layered structure using 2-(2-hydroxyphenyl) benzothiazole (HBT) and poly (N-vinylcarbazole) (PVK) as the emitting layer (EML) and the hole transport layer (HTL) respectively, could realize the blue-green light emission. Bis-(2-(2-hydroxyphenyl) benzothiazole)zinc (Zn(BTZ)2), synthesized with zinc acetate dihydrate and HBT to form a complex, is used as main EMLs in a similar structure to fabricate devices B and C. Bright and pure white light emissions can be obtained from device C which was fabricated with a green-white emitting host Zn(BTZ)2 and red dopant 5,6,11,12-tetraphenylnaphthacene (rubrene). The maximum quantum efficiency of device C could reach 0.63%, and the corresponding brightness and CIE coordinates were 4000cd/m2 and (x= 0.341, y= 0.334) at the driving voltage of 20V.
|
72 articles
|