碰撞诱导钠分子A1Σ+u→X1Σ+g的荧光光谱

用532.0 nm激光激发Na2分子到B1Πu电子态,记录了Na(3P)原子的跃迁和Na2分子的A1Σ+u-Χ1Σ+g的谱带.由Na与Na2激发态发射的光谱及其强度可以认定在Na-Na2系统中的碰撞过程,Na(3P)原子线是Na2(B1Πu)到Na(3P)的碰撞能量转移产生的,预解离过程也可产生原子线.而A1Σ+u-Χ1Σ+g谱带是由B1Πu到21Σ+g的碰撞转移后再由21Σ+g到A1Σ+u的辐射而引起的.在360℃,根据辐射衰变率和荧光强度,得到Na2(B1Πu)到Na2(21Σ+g)碰撞转移率系数为7.1×10-10 cm3s-1,而B1Πu的预解离率为2.3×106 s-1.     

钠分子B 1Πu与2 1Σ+g间的碰撞激发转移

用HeCd激光器的4416nm线激发Na2分子到B1Πu电子态,记录了Na原子的跃迁和Na2分子的A1Σ+u-Χ1Σ+g的谱带。由Na与Na2激发态发射的光谱及其强度可以认定在NaNa2系统中的碰撞过程,Na原子线是Na2(B1Πu)到Na(3P)的碰撞能量转移产生的,预解离过程也可产生原子线。而A1Σ+u-Χ1Σ+g谱带是由B1Πu到21Σ+g的碰撞转移后再由21Σ+g到A1Σ+u的辐射而引起的。在360℃,根据辐射衰变率和荧光强度,得到Na2(B1Πu)到Na2(21Σ+g)碰撞转移率系数为57×10-10cm3·s-1,而B1Πu的预解离率为27×106s-1。     

Cs_2(B~1Π_u)态与基态Cs原子间的碰撞激发转移

在Cs2密度约为2×1013 cm-3的纯Cs样品池中,脉冲激光激发Cs2(X1 Σg+)至B 1Πu态,利用原子和分子荧光光谱方法研究了Cs2(B 1Πu)+Cs(6S)的碰撞激发转移过程.用736 nm激发Cs2到B 1Πu(v＜10),这时预解离不发生.由B 1Πu→X1 Σg+时间分辨跃迁信号得到B 1Πu态的辐射寿命为(35±7)ns,B1Πu态与Cs原子碰撞转移总截面为(4.0±0.5)×10-14 cm2.用705 nm激发至B 1Πu(v＞30)态,这时发生预解离,在不同的Cs密度下,测量了I(D1),I(D2)和分子带的时间积分荧光的相对强度,得到了预解离率为(4.3±1.7)×105 s-1(对预解离到6P3/2)和(4.7±1.9)×106 s-1(对预解离至6P1/2);碰撞转移截面为(0.45±0.18)×10-14 cm2(对转移到6 P1/2)和(4.3±1.7)×10-14 cm2(对转移到6P3/2).结果表明,如果B 1Πu(v)是束缚的,6P原子由碰撞转移产生;如果B 1Πu(v)是预解离的,则6P原子由预解离和碰撞转移产生.     

S_2(B~3Σ_u~-→X~3Σ_g~-(ν′≥18,0))弥散谱带的自旋-轨道从头计算

采用从头计算方法从理论上解释了实验中双原子分子S_2(B~3Σ_u~-→X~3Σ_g~-吸收谱中谱带(18,0)开始出现的弥散现象.计算了包含自旋-轨道耦合(SOC)的B3Σu-和排斥的15Πu,23Σu 态的电子势能曲线.对于(18,0)谱带开始弥散,给出了与其他文献不同的物理解释.计算结果表明B3Σu-与15Πu,23Σu 态的SOC作用导致预解离对谱带的弥散起着决定作用,并与实验结果作了比较,符合很好.     

AlF的X1Σ+,A1Π和B1Σ+态的势能函数

使用SAC/SAC-CI和D95 、6-311 g及D95(d)等基组,分别对AlF的基态X1Σ 、第一简并激发态A1Π和第二激发态B1Σ 的平衡结构和谐振频率进行了优化计算.对所有计算结果进行比较,得出D95(d)基组为最优基组;运用D95(d)基组和SAC方法对基态X1Σ ,SAC-CI方法对激发态A1Π和B1Σ 进行单点能扫描计算,并用正规方程组拟合Murrell-Sorbie函数,得到了相应电子态的势能函数解析式,由得到的势能函数计算了与X1Σ 、A1Π和B1Σ 态相对应的光谱常数,结果与实验数据较为一致.     

Na_2分子X~1Σ_g~ ,A~1Σ_u~ 和B~1Π_u态的势能函数

使用SAC/SAC-CI方法,利用6-311 g,6-311g**及cc-PVTZ等基组,对Na2分子的基态(X1Σg )、第一激发态(A1Σu )和第二激发态(B1Πu)的平衡结构和谐振频率进行计算.通过对3个基组的计算结果的比较,得出6-311g**基组为3个基组中最优基组的结论;使用6-311g**基组,分别利用SAC的GSUM(Group Sum of Operators)方法对基态(X1Σg ),SAC-CI的GSUM方法对激发态(A1Σu )和(B1Πu)进行单点能扫描计算,用正规方程组拟合Murrell-Sorbie函数,得到相应电子态的完整势能函数.用得到的势能函数计算与基态(X1Σg ),第一激发态(A1Σu )和第二激发态(B1Πu)相对应的光谱常数(Be,αe,ωe和ωeχe),结果与实验数据基本吻合.     

弯曲振动对CS_2分子~1B_2(~1Σ_u~+)态预解离寿命的影响

在209.5～216nm,采用光解碎片激发(PHOFEX)谱技术,对CS2分子1B2(1Σ+u)态预解离寿命进行了 考察.测量在超声射流中进行.信号来自解离碎片CS(A1Π,v′=0←X1Σ+,v″=0)Q支带头的激光诱导荧光 (LIF).预解离寿命是通过对谱带进行拟合来提取的.拟合中假定基态转动布居为Boltzmann分布,寿命加宽的转 动谱线为Lorentz线形.通过拟合共获得1B2(1Σ+u)态13个跃迁所对应的预解离寿命,其中6个数据是新得到的. 结果表明,基态振动角动量量子数l或激发态转动角量子数K(K=l)对预解离寿命有明显的影响.对于激发态的 同一振动能级,较大的K对应于较短的预解离寿命.实验中采用可加热的射流喷嘴,用以提高热带激发的强度, 以改善对较大转动角量子数K的影响的考察.     

S2(B 3∑u-→X3∑g-(v''''≥18,0))弥散谱带的自旋-轨道从头计算

采用从头计算方法从理论上解释了实验中双原子分子S2(B3∑u-→X3∑g-)吸收谱中谱带(18,0)开始出现的弥散现象.计算了包含自旋-轨道耦合(SOC)的B3∑u-和排斥的15∏u,23∑u+态的电子势能曲线.对于(18,0)谱带开始弥散,给出了与其他文献不同的物理解释.计算结果表明B3∑u-与15∏u,23∑u+态的SOC作用导致预解离对谱带的弥散起着决定作用,并与实验结果作了比较,符合很好.     

Na2(A1∑u+,v=8～b3Ⅱ0u,v=14)-Na体系转动传能的碰撞量子干涉效应

沙国河及其工作组于1995年发表了CO A1Π(v=0)～e3∑-(v=1)与He1,Ne及其它碰撞伴的碰撞过程中转动传能的碰撞量子干涉现象,并得到了积分干涉角,陈等从理论和实验上发现了Na2(A1∑u ,v=8～b3Π0u,v=14)体系与Na(3s)碰撞的碰撞量子干涉现象,孙等计算了其积分干涉角,但是对微分干涉角没有过多的计算.本文作为对原子-双原子体系碰撞诱导转动传能的进一步理论研究,在含时一级波恩近似的基础上考虑各向异性相互作用势和长程相互作用势,计算了单叁混合态的Na2(A1∑u ,v=8-bΠ0u,v=14)体系与Na碰撞的微分干涉角,并得到了微分干涉角与碰撞参数的关系,此理论模型对理解和进行分子束实验是非常重要的.     

852.3 nm激光线共振激发Cs蒸气的荧光光谱

研究了Cs蒸气被单模半导体激光器的852.3 nm线激发产生的荧光光谱.由Cs,Cs2的荧光及其强度确定了在受激Cs-Cs2系统中的若干碰撞和辐射过程.高位态原子线是由Cs(6P3/2) Cs(6P3/2)到Cs(6D,8S)的碰撞能量合并形成的,cs2(B1Ⅱu)带则由cs(6P) cs2(X1Σg )碰撞转移产生.通过激发转移、能量碰撞合并和Cs2-Cs碰撞传能研究了62P原子的精细结构混合,得到了6P3/2→6P1/2碰撞转移速率系数是(5.2士2.1)×10-11 cm3·s-1,给出了过程Cs2(B1Ⅱu) Cs(6S)→cs2(X1Σg ) cs(6P1/2)的速率系数是(1.0±0.4)×10-9 cm3·s-1.     

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].     

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.     

Real-time restoration of rotational blurred image using gradient-loading

The key to the restoration of rotational motion blurred image is how to restore the image under a low cost and to correct the irreversibility of the degradation function matrix.Based on the special qualities of degradation function matrix and precise deduction in space-domain, we present a new approach using gradient-loading for restoration of rotational blurred image.By easily adding a gradient operator, the irreversibility of the original matrix is corrected and can be applied for inverse filtering then.Gradientloading is the optimized approach which combines the advantages of both the approaches using constrained least square filtering and traditional diagonal-loading.Compared with the approach using least square filtering, its peak signal-to-noise ratio (PSNR) is improved from 3.18 to 6.46dB, while the computing time is reduced to 1/2-1/3.Experimental results demonstrate the effectiveness, noise-resistibility, robustness, and low complexity of this approach, which make it more suitable for real-time environment.     

All-Optical Logic Device Using Bent Nonlinear Tapered Y-Junction Waveguide Structure

We propose an all-optical logic device made of a bent tapered Y-junction waveguide with a Kerr-type nonlinear interface. It could provide an AND gate, OR gate, and exclusive-OR (XOR) gate. We could obtain different transmission results by adjusting the bending angle. The numerical simulation results show that the device functions as AND, OR, and XOR gates.     

Real-time, continuous-wave terahertz imaging by a pyroelectric camera

Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.