对23P2介子九重态中同位旋标量成员的质量分析

基于实验上已经确认的基态张量介子九重态的安排和现有的实验数据,利用从雷吉轨迹理论和质量混合矩阵推导出的介子质量关系,对张量介子第一径向激发态的安排做了分析预测.根据得到的结果,可以推测f₂（1810）和f₂（2010）可能作为张量介子第一径向激发态的候选者.同时给出了f₂（1810）和f₂（2010）作为张量介子第一径向激发态时的衰变信息.这些结论对激发态张量介子,特别是其中的同位旋标量态的安排将提供帮助.     

Recombination during expansion of ultracold plasma

Signals of ultracold plasma are observed by two-photon ionization of laser-cooled caesium atoms in a magneto-optical trap. Recombination of ions and electrons into Rydberg atoms during the expansion of ultracold plasma is investigated by using state-selective field ionization spectroscopy. The dependences of recombination on initial electron temperature (1--70 K) and initial ion density ($ \sim $10$^{10}$ cm$^{ - 3})$ are investigated. The measured dependence on initial ion density is $N^{1.547\pm 0.004}$ at a delay time of 5 $\mu $s. The recombination rate rapidly declines as initial electron temperature increases when delay time is increased. The distributions of Rydberg atoms on different values of principal quantum number $n$, i.e. $n=30$--60, at an initial electron temperature of 3.3 K are also investigated. The main experimental results are approximately explained by the three-body recombination theory.     

ZnO纳米棒的低温溶液法制备、光电特性研究及其在有机/无机复合电致发光中的应用

利用水热法制备了垂直于衬底的定向生长的ZnO纳米棒,利用扫描电子显微镜及光致发光的方法对其形貌及光学特性进行了表征,利用场发射性能测试装置对ZnO纳米棒的场发射性能进行了测试.结果表明:利用水热法在较低的温度(95 ℃) 下生长了具有较好形貌和结构的ZnO纳米棒,并表现出了较好的场发射特性,当电流密度为1 μA/cm²时,开启电场是2.8 V/μm,当电场为6.4 V/μm时,电流密度可以达到0.67 mA/cm²,场增强因子为3360.稳定性测试表明,在5 h内,4.5 V/μm的电场下,其波动不超过25%.将制备的ZnO纳米棒应用到有机/无机电致发光中,其中ZnO纳米棒为电子传输层,m-MTDATA(4,4',4″-tris{N,(3-methylphenyl)-N-phenylamino}-triphenylamine) 为空穴传输层,得到了ZnO的342 nm的紫外电致发光,此发光较ZnO纳米棒光致发光的紫外发射有约40 nm的蓝移. 关键词： ZnO纳米棒 场发射 水热法 有机/无机复合电致发光     

Cs 39D态Rydberg原子Stark光谱的实验研究

本文从理论和实验上对Cs39D态Rydberg原子在弱电场作用下的Stark效应做了详细研究. 理论上利用数值方法计算了Cs原子39D态的Stark结构;实验上,采用两步激发超冷基态原子获得超冷Rydberg原子,通过场电离的方法获得了39D态的Stark光谱,测量获得α^5/2₂,α^5/2₀,α^3/2₂和α^3/2₀相应的极化率分别为：62(7),－146(13), 73(6) 和－106(20) MHz·V^-2cm²,实验结果与理论相符合.     

Photonic true-time delay unit for broadband adaptive nulling in antenna arrays

An Opto-VLSI-based (VLSI: very-large-scale-integration) tunable true-time delay (TTD) generation unit used for adaptive null steering in phased array antennas is presented. The system is based on continuous tunable optical TTD technique. Arbitrary multiple true-time delays to generate multiple broadband nulls can simultaneously be synthesised for each antenna element. The proposed structured are characterised both theoretically and experimentally. Experimental results demonstrating the principle of the true-time delay for null generations are presented. The maximum time delay measured for a wavelength tuning from 1530 to 1560 nm is 9.5 ns.     

Microstructure and dielectric properties of PMN–PT ceramics prepared by the molten salts method

The sintering characteristic and dielectric properties of 0.67PMN–0.33PT ceramics prepared by the molten salt synthesis (MSS) method were investigated. PMN–PT particles synthesized by MSS with smaller grain size and good dispersion could lower the sintering temperature of ceramics; PMN–PT ceramics with relative density above 96% could be obtained in the range 1150–1180 °C. The molten salts species could significantly affect the microstructure and properties of MPN-PT ceramics. In the range 1100–1200 °C, PMN–PT ceramics from the sulfate flux MSS powders showed intergranular fracture, but that from the chloride flux MSS powder showed transgranular fracture. At the same sintering condition, the properties of PMN–PT ceramics from the powders prepared in the chloride flux are better than that from the powders prepared in the sulfate flux, their maximum dielectric constant ε_max≈29,385 and piezoelectric constant d₃₃≈660 pC/N. The above results demonstrated that PMN–PT ceramics prepared by the molten salts method possessed excellent piezoelectric and dielectric properties.     

Deterministic secure quantum communication using four-particle genuine entangled state and entanglement swapping

A deterministic secure quantum communication scheme using entanglement swapping is proposed. The sender prepares four-particle genuine entangled states and sends two particles in each state to the receiver and remains the rest particles. If the quantum channel is secure, they begin to communicate. After their four-particle projective measurements, the receiver can obtain the secret information according to his measurement outcomes and classical information from the sender. Using entanglement swapping, there are no particles carrying secret information to be transmitted.     

Electronic structure calculations for BaSxSe1−x alloys

A series of first principles calculations have been carried out to study structural, electronic properties of BaS_xSe_1−x alloys. We have used the local density as well as the generalized gradient approximations for the exchange-correlation potential. The structural properties of these materials, in particular the composition dependence to the lattice constant and bulk modulus, are found to be linear. It is also found linear relationship between theoretical band gaps and 1/a² (where a is lattice constant).     

Up-conversion emissions of Er<Superscript>3+</Superscript>-Yb<Superscript>3+</Superscript> codoped Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles by the arc discharge synthesis method

The Er³⁺-Yb³⁺ codoped Al₂O₃ nanoparticles with an average particle size of about 50 nm have been synthesized by an arc discharge synthesis method. The green and red up-conversion emissions centered at about 526, 547 and 677 nm, corresponding respectively to the ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 transitions of Er³⁺, were detected by a 978-nm semiconductor laser diode excitation. The Annealing has evident effect on the up-conversion emissions of the samples: The red up-conversion emission is noticeable before annealing; however, the green up-conversion emission becomes predominant after annealing. The mixture of (Er,Yb)₃Al₅O₁₂ and α-(Al,Er,Yb)₂O₃ phases is more favorable for green up-conversion emissions due to an enhancement of the ESA (I) of ⁴I_11/2+a photon→⁴F_7/2 and ET (III) of ²F_5/2(Yb³⁺)+⁴I_11/2(Er³⁺)→²F_7/2(Yb³⁺)+⁴F_7/2(Er³⁺) processes. The two-photon absorption up-conversion process is involved in the green and red up-conversion emissions. The results have proved that arc discharge synthesis is a new promising preparation technology for optical materials. Supported by National Natural Science Foundation of China (Grant No. 10804015), the Scientific Research Foundation for Doctor of Liaoning Province (Grant No. 20071095), and the Educational Committee Foundation of Liaoning Province (Grant No. 2008123)