Sr原子|M|=1电场标度能谱

通过同步改变激光扫描波长和外加电场大小,保持标度能为常量,将Sr原子从基态激发到|M|=1的激发态,得到了标度能ε=-3.00,-2.50,-1.88时的常数标度能谱.实验傅里叶变换回归谱与氢原子闭合轨道理论计算进行了比较,峰值位置符合较好,峰值强度则受Sr原子实效应影响较大.     

电场中Rydberg原子的常数标度能谱方法

标度能谱理论能够简化外场谱及可以经典方法理解原子外场谱而倍受关注。本文报道了用于电场中Rydberg原子常数标度能谱实验研究的装置以及有关的计算机控制、采集及处理系统。该系统对能量E和电场F进行同步控制以保持标度能谱ε=E/F为常数，并成功地得到Rydberg态Sr原子在标度能ε=-3.0时的标度能谱，经过傅里叶变换，获得了电场中Sr原子的电子回归谱。     

Ba Rydberg原子M = 0电场常数标度能谱

选择激光偏振方向，同步改变激发激光的波长(即原子的激发能量E）和外加电场强度 F，使标度能ε=E/F保持为常数，得到了原子束中Ba Rydberg原子在标度 能ε=-300时M=0激发的常数标度能谱.由实验标度能谱的Fourier变换得到的回 归谱与氢的均匀化近似后的闭合轨道理论计算相比较，发现实验回归谱的峰值位置与理论计 算符合较好，而峰值强度则与理论相差较大，分析认为是由于受到核散射和双电子微扰态的 影响所致. 关键词： 标度能谱 闭合轨道理论     

Sr原子的电场标度能谱

利用原子束 -激光束 -电场相互垂直交叉的实验构型 ,通过同步改变激光激发波长和外加电场强度 ,得到了Sr原子在标度能为 - 3.0时的常数标度能谱。通过对实验谱进行傅里叶变换得到的电子回归谱的分析 ,发现在分岔附近回归峰强度增大。均匀化近似闭合轨道理论计算谱与实验回归谱进行了比较 ,发现在低作用量处两者较好符合。     

(La0.7Sr0.3MnO3)m(BiFeO3)n超晶格间隔的La0.7Sr0.3MnO3三明治结构制备及表征

采用射频磁控溅射的方法在SrTiO3(001,基片上制备了(La0.7Sr0.3MnO3)m(BiFeO3)n超晶格间隔的La0.7Sr0.3MnO3三明治结构.X射线衍射分析证明(La0.7Sr0.3MnO3)m(BiFeO3)n具有明显的超晶格结构.电流垂直于薄膜表面测得的电阻-温度关系表明.La0.7Sr0.3MnO3)m(BiFeO3)n超晶格薄膜在290 K有金属-绝缘体转变,略低于单层La0.7Sr0.3MnO3薄膜的转变温度.电流在0.01-10 mA范围内,观察到薄膜的峰值电阻随电流增大而减小,峰值变化率远大于单层La0.7Sr0.3MnO3薄膜,且随着超晶格周期厚度的增加而增大.低温下,电流-电压曲线表明其导电机制应主要为空间载子限制,且显示较大的电压偏置,表现出肖特基结的特性.     

La0.9Sr0.1MnO3薄膜中电流效应研究

用直流磁控溅射法在(100)LaAlO3衬底上制备了La0.9Sr0.1MnO3薄膜.经退火处理后薄膜的原子力显微镜形貌观测和X射线衍射分析显示具有比较好的质量.电阻率-温度关系表明La0.9Sr0.1MnO3薄膜在281 K处发生金属绝缘体转变.电流在0.01-4 mA范围内,薄膜的峰值电阻率随电流增大而减小,在4 mA下获得了30.5%的峰值电阻率变化率,并从相分离图像给出了简单解释.     

(Pr,Nd)_(2/3)Sr_(1/3)MnO_3体系中的低温比热反常现象

主要研究了(Pr1-yNdy)2/3Sr1/3MnO3体系多晶样品在低温下的比热反常现象.Pr2/3Sr1/3MnO3在低温下没有比热反常现象,但随着Nd替代Pr,比热反常开始出现,峰值逐渐增加,峰值出现温度逐渐减小;在磁场的作用下,峰值减小,峰值出现温度逐渐增加;经分析,该低温比热反常现象与Schottky效应相关.     

熔融织构的YBCO超导体的交流磁化率频率响应

在涡漩玻璃理论的基础上,我们推导出了交流磁化率的虚部峰值温度和频率的标度方程,可表示为Tp=Cf1/(v(z-1)).实验结果表明我们的标度方程和实验符合得很好.利用标度方程可以确定样品在磁场下的涡漩玻璃转变温度Tg和指数v(z-1)的数值.     

复合胶体喷雾自组装Sr2Al2SiO7:Eu2+荧光体及其发光特性

采用AlOOH/Sr(NO3)2/SiO2/Eu复合胶体喷雾工艺制备了D50=3.83μm球形Sr2Al2SiO7:Eu2 梯次结构荧光粉.复合胶体喷雾过程形成雾滴,雾滴中纳米粒子组分在表面张力及毛细管力作用下自组装形成梯次结构干凝胶粉.干凝胶粉经1300 ℃灼烧得到梯次结构Sr2Al2SiO7:Eu2 荧光粉.X射线衍射(XRD)分析及晶格常量计算结果表明,Eu2 离子部分取代Sr2 格位进入Sr2Al2SiO7晶格.Sr2Al2SiO7:Eu2 荧光体激发谱由峰值位于326 nm附近的宽带构成,属于Eu2 的4f→5d跃迁吸收带;发射光谱峰值波长位于约500 nm处,属于Eu2 离子4f65d到4f7跃迁导致的宽带发射.     

Bi_2Sr_2CaCu_2O_(8+δ)单晶的钉扎力标度和磁通钉扎机制

测量了 Bi2 Sr2 Ca Cu2 O8+δ单晶不同温度下的磁化曲线。根据 Bean临界态模型得到了不同温度下的钉扎力密度 FP 对磁场的依赖关系 ,发现在不同温度下的钉扎力密度可以标度在同一条曲线上。标度函数和最大钉扎力所对应的磁场与不可逆场 Hirr的比值都表明 Si2 Sr2 Ca Cu2 O8+δ单晶在磁通玻璃态的钉扎机制主要是正常相面钉扎。     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.