苯乙腈的单色共振增强双光子电离光谱及其Franck-Condon模拟

苯乙腈广泛应用于医药、农药、染料、光电材料和喹啉衍生物的合成,在相关领域备受关注.本文采用超声分子束技术获得了苯乙腈的单色共振双光子电离光谱,确定了该分子的激发能为(37646±2) cm^–1.结合密度泛函理论计算和Franck-Condon模拟,详细分析了测量的振动频率,给出了尽可能准确的光谱归属.理论和实验结果都表明,光谱的低频区域信号强、背景低、分辨率好,而高频范围表现出相反特征.许多谱带被确认,大部分属于芳香环平面内的振动,理论计算表明这与跃迁过程中芳香环的扩张有关.     

四氯化碳费米共振的拉曼光谱研究

费米共振现象是一种广泛存在于分子振动光谱中的现象,特别是结构比较复杂的多原子分子.在多原子分子中当振动倍频或组合频位于某一基频附近,由于发生振动耦合,会出现两个新峰,峰的位置向两侧发生移动,二者谱线强度发生变化,把这种现象称为费米共振.费米共振现象不仅存在于红外光谱中,也存在于拉曼光谱中.文章中测量了CCl4的拉曼光谱,利用所得到的谱线峰位和用Originpro7.5软件程序获得积分强度,用费米共振的相关理论计算了C-Cl的a1对称伸缩振动频率v1与C-Cl2的f对称弯曲振动频率v4的组合频(v1 v4)与(某一未知基频)C-Cl的f对称伸缩振动频率v03的费米共振特征参数,进而计算出了耦合系数W和这一未知基频v03.该文对理解费米共振,了解分子振动频率,研究分子结构有很重要的参考价值.     

对甲氧基苯甲腈的单色共振双光子电离光谱

对甲氧基苯甲腈是一种重要的化学化工原料,本文采用超声分子束技术和共振多光子电离方法获得了对甲氧基苯甲腈的单色共振双光子电离光谱,基态S0到电子激发态S1的0←0跃迁被确定为(35549±2)cm~(-1),结合含时密度泛函理论计算结果对观察到的光谱进行了振动模式标识和描述.实验发现呼吸振动模非常易于激活,其基频和二次泛频光谱很强,三次泛频也可明确标识,观察到大量呼吸振动与其他正则模的结合振动,这是对甲氧基苯甲腈不同于常见的多原子分子的一个重要特性.这些结果为研究对甲氧基苯甲腈的里德堡态、动力学和零动能光谱等提供了重要的参考数据.     

分子费米共振拉曼光谱强度分析

测量了CCl₄和CS₂分子的Raman光谱。用Bertran理论和群论等相关理论对其光谱强度进行了分析,获得了发生费米共振分子的拉曼光谱强度的特殊规律： (1)发生费米共振的基频和倍频(和频)间发生能量转移,两光谱强度大小相互接近,当发生费米共振的基频和倍频(和频)间距离很小时,两发生费米共振的光谱强度相等(R=1);(2)能出现倍频光谱强度高于其基频光谱强度;(3)也会观测到费米共振光谱,而观测不到参与费米共振的和频中的基频光谱。此研究对化学、材料科学中的分子结构、材料成分等研究中的谱线认证、归属有很好的参考价值。     

SF2自由基4s和(C)态的共振增强多光子电离研究

利用六氟化硫和氩气混合样品直流脉冲放电产生SF2自由基,观测得到320-365nm波长范围内SF2自由基的(2+1)共振增强多光子电离(REMPI)光谱.经分析,该REMPI谱对应于SF2自由基的4s(1B1)Rydberg态和(C)态的共振双光子吸收,获得了二个态的全对称伸缩振动模(ω('1))和OPLA模(ω('2))的振动频率值.初步澄清了(C)态的带源及振动属性,并对(C)态附近SF2自由基的解离行为进行了讨论.     

SF2自由基4s和C态的共振增强多光子电离研究

利用六氟化硫和氩气混合样品直流脉冲放电产生SF2自由基,观测得到320—365nm波长范围内SF2自由基的(2+1)共振增强多光子电离(REMPI)光谱.经分析,该REMPI谱对应于SF2自由基的4s(B1B1)Rydberg态和态的共振双光子吸收,获得了二个态的全对称伸缩振动模(ω′1)和OPLA模(ω′2)的振动频率值.初步澄清了态的带源及振动属性,并对态附近SF2自由基的解离行为进行了讨论 关键词：     

SF_2自由基4s和态的共振增强多光子电离研究

利用六氟化硫和氩气混合样品直流脉冲放电产生SF2 自由基 ,观测得到 3 2 0— 3 65nm波长范围内SF2 自由基的 ( 2 1)共振增强多光子电离 (REMPI)光谱 .经分析 ,该REMPI谱对应于SF2 自由基的 4s( B1B1)Rydberg态和 C态的共振双光子吸收 ,获得了二个态的全对称伸缩振动模 (ω′1)和OPLA模 (ω′2 )的振动频率值 .初步澄清了 C态的带源及振动属性 ,并对 C态附近SF2 自由基的解离行为进行了讨论     

SF2自由基3d,5s里德伯态的实验确认

利用自行研制的脉冲直流放电装置产生SF₂自由基，结合共振增强多光子电离(REMPI)技术，研究了27—294nm范围内SF₂自由基(2+1)REMPI激发谱，获得了SF₂自由基3d,5s里德伯态相应的带源及被激活的对称伸缩振动模的振动频率，并估算了这些态的量子亏损值． 关键词：     

基于共振增强多光子电离技术的慢电子速度影像应用

利用激光共振增强多光子电离技术,我们既可以观察中性物种激发态的振动结构也可以获得相应正离子的高分辨电子能谱.采用自行研制的双静电透镜系统对Xe原子在258.00 nm激光束下的三光子电离过程展开研究,优化得到飞行时间质谱的质量分辨率(m/Δm)达到1300,慢电子速度成像的电子能量分辨率(ΔE/E)为2.4%,阈值电子能量分辨优于1 me V.在该条件下,开展了分子的电子谱研究,研究了苯的激发电子态共振增强双光子电离光谱和振动态选择的苯正离子的慢电子速度成像谱,通过对谱线归属,获得了1B2u激发态的振动序列和苯正离子的振动能级结构信息.     

对氯苯腈的双色共振双光子电离和质量分辨阈值电离光谱

本文利用双色共振双光子电离和质量分辨阈值电离光谱技术,研究了对氯苯腈分子第一电子激发态S₁和离子基态D₀的振动特征,确定了对氯苯腈分子S₁←S₀电子跃迁的激发能为35818±2 cm^–1,精确的绝热电离能为76846±5 cm^–1.对氯苯腈分子³⁵Cl和³⁷Cl两种同位素有相同的激发能和电离能以及相似的振动特征.采用高精度密度泛函方法,计算了对氯苯腈分子在中性基态S₀、第一电子激发态S₁、离子基态D₀的结构参数和振动频率,分析了电子激发和电离过程中对氯苯腈分子结构和振动频率的变化,并对激发态和离子基态的振动光谱进行了归属,振动光谱上的活性振动大多数是苯环平面内的弯曲振动.通过比较对氯苯酚、对氯苯胺、对氯苯甲醚、对氯苯腈与苯酚、苯胺、苯甲醚、苯腈分子的跃迁能,分析了取代基Cl原子与苯环之间的相互作用及其对分子跃迁能的影响.     

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.