Normally-Ordered Time Evolution Operator for Mass-Varying Harmonic Oscillator and Wigner Function of Squeezed Number State

For investigating dynamic evolution of a mass-varying harmonic oscillator we constitute a ket-bra integration operator in coherent state representation and then perform this integral by virtue of the technique of integration within an ordered product of operators. The normally ordered time evolution operator is thus obtained. We then derive the Wigner function of u（t）｜n,〉, where ｜n〉 is a Fock state, which exhibits a generalized squeezing, the squeezing effect is related to the varying mass with time.     

Preserving Coherence of Coherent State Studied via Weyl-Wigner Correspondence

By means of the Weyl correspondence and the explicit normally ordered expression of the Wigner operator we convert the time evolution equation of coherent states, governed by some Hamiltonian operators, into seeking for consistent solution of a set of evolution equtions of classical variables which can meet the requirment that an initial coherent state remains coherent all the time.     

Operator Formulas Involving Generalized Stirling Number Derived by Virtue of Normal Ordering of Vacuum Projector

By virtue of the normal ordering of vacuum projector we directly derive some new complicated operator identities, regarding to the generalized Stirling number.     

Evolution of Number State to Density Operator of Binomial Distribution in the Amplitude Dissipative Channel

We show that passing through the amplitude dissipative channel the initial pure number state density operator is evolved into the density operator of binomial distribution （a mixed state）, and the binomial distribution parameter is just equal to e^-2kt, where k is the dissipative parameter of the channel. We solve the corresponding master equation to obtain the operator-sum representation of the density operator by virtue of the entangled state representation, which seems to be a convenient approach.     

Neutron Spectroscopic Factors of ^7Li and Astrophysical ^6Li（n,γ）^7Li Reaction Rates

Angular distributions of the ^7Li（^6Li, ^6Li）^7Li elastic scattering and the ^7Li（^6Li, ^7Lig.s.）^6Li, ^7Li（^6Li, ^7Li0.48）^6Li transfer reactions at Ec.m. = 23.7 MeV are measured with the Q3D magnetic spectrograph. The optical potential of ^6Li ＋ ^7Li is obtained by fitting the elastic scattering differential cross sections. Based on the distorted wave Born approximation （DWBA） analysis, spectroscopic factors of ^7Li =^6Li n are determined to be 0.73 ± 0.05 and 0.90 ± 0.09 for the ground and first exited states in ^7Li, respectively. Using the spectroscopic factors, the cross sections of the ^6 Li（n, γ0,1）^7 Li direct neutron capture reactions and the astrophysical ^6Li（n, γ）^7 Li reaction rates are derived.     

A Phase-Controlled Optical Parametric Amplifier Pumped by Two Phase-Distorted Laser Beams

We theoretically study the phase characteristic of optical parametric amplification （OPA） or chirped pulse OPA （OPCPA） pumped by two phase-distorted laser beams. In the two-beam-pumped optical parametric amplification （TBOPA）, due to spatial walk-off, both of the pump phase distortions will be partly transferred to signal in a single crystal so as to degrade the signal beam-quality, which will be more serious in high-energy OPCPA. An OPA configuration with a walkoff-compensated crystal pair is demonstrated for reducing the signal phase distortion experienced in the first stage and ensuring the signal phase independent of two pump phase distortions through the second crystal, hence maintaining the signal beam-quality. Such a TBOPA is similar to the conventional quantum laser amplifier by means of eliminating its sensitivity to the phase and number of the pump beams.     

中国北方古建油饰彩画中绿色颜料的光谱分析

古建油饰彩画中颜料成分的分析鉴定是古建维修、保护的重要基础工作。文章利用X射线荧光分析、X射线衍射分析、扫描电镜-能谱分析技术,首次系统地分析检测了来自北京、山西、甘肃等中国北方地区的27个古建油饰彩画中的绿色颜料。结果表明,其中15个样品使用了巴黎绿这种含铜、砷的人工合成颜料,其余样品未检测出矿物颜料,显色成分应为人工合成的有机物。在所有分析样品中未检测到古代常用的绿色颜料石绿和氯铜矿的存在。该研究工作开辟了光谱分析技术应用于古建油饰彩画颜料鉴定的新领域,为该类文物分析鉴定、修复材料的选择提供了科学数据。     

光源稳定性对简并四波混频信噪比影响的实验研究

在碘蒸气中研究了染料激光稳定性对简并四波混频(DFWM)信噪比的影响。实验中采用多模Nd∶YAG激光器倍频的输出泵浦染料激光器(染料PM580溶于酒精)。在具有前向补偿分光系统和图像探测系统的帮助下,在常温常压条件下测得泵浦光在波长为554.013 nm时达到饱和光强为290 μJ。同时发现染料激光器的光稳定性(输出波长范围,光束质量和能量转换效率等)随使用时间,泵浦激光脉冲次数和能量的增加而逐渐减弱。另外通过对比发现在染料激光器输出不稳定时,光源单色性和指向性等指标的变化导致在同一泵浦强度不同时刻获得的DFWM信号强度相差很大,且DFWM信号信噪比低。染料激光器光源稳定性对DFWM信号影响的研究结果对物质的痕迹量探测以及无荧光物质光谱定标等方面的应用具有重要意义。     

利用偏最小二乘回归从冬小麦冠层光谱提取叶片含水量

通过人为控制灌溉水平,在冬小麦3个发育期(孕穗、开花、乳熟)测定了冠层光谱和叶片含水量(leaf water content,LWC)。针对每期数据,结合偏最小二乘回归和迭代特征去除,建立了基于诊断波段的LWC回归模型。结果表明,叶片水分的光谱响应及反演精度受小麦生长状态的影响。在孕穗、开花和乳熟3个发育阶段,回归模型中光谱数据的最佳利用形式分别为对数光谱、导数光谱和反射率光谱;重要光谱区间为SWIR,NIR和SWIR;模型交叉验证决定系数(R2_CV)为0.750,0.889和0.696。研究结论对今后监测冬小麦旱情和开发作物水分遥感产品具有重要的指导作用。     

Composition-Dependent Characterization of Sb2Te3 Thin Films Prepared by Ion Beam Sputtering Deposition

The optimization of ion beam sputtering deposition process for Sb2 Te3 thin films deposited on BK7 glass substrates is reported. The influence of composition ratio on the thermoelectric properties is investigated. X-ray diffraction shows that the major diffraction peaks of the films match with those of Sb2 Te3. Hall effect and Seebeck coefficient measurement reveal that all the samples are of p-type. The Sb2 Te3 thin films exhibit the Seebeck coefficient of 190μVk^-1 and the electrical conductivity of 1.1 × 10^3 Scm^-1 when the atomic ratio of Sb to Te is 0.65. Carrier concentration and motility of the films increase with the increasing atomic ratio of Sb to Te. The Sb2 Tea film with a maximum power factor of 2.26×10^-3 Win^-1K^-2 is achieved when annealed at 400℃. Raman measurement shows that the main peaks are at about 120 cm^-1, 252 cm^-1 and 450 cm^-1, in agreement with those of V-VI compound semiconductors.