深冷中性铝团簇的产生和光电离

报道了用激光蒸发／分子束方法产生深度冷却的中性金属团簇。产生的铝团簇Ａｌ．（ｎ＝２，……，６，７）用１９３ｎｍ的准分子激光电离，由飞行时间质谱（ＴＯＦＭＳ）探测。对激光蒸发／分子束技术产生的团簇束的特点作了简单评述并与其它团簇源作了比较。     

飞行时间质谱峰形分析

报道了在用脉冲355 nm的YAG激光对水/甲醇二元团簇的多光子电离飞行时间质谱研究中,发现在电离激光相对于脉冲分子束的不同延时或是同一延时下不同的激光能量下,测得的离子谱峰除强度变化外,峰值发生漂移.离子峰值漂移的大小与信号强度密切相关.信号强度越大,离子的飞行时间越短,峰值漂移越大.分析认为:这种峰值漂移不是因为新质量数谱峰的出现,而是离子在穿越质谱仪的离子引出区和加速区极板时发生部分离子吸附,引起极板间电压的起伏造成的.离子信号越强,意味着极板对离子吸附的量越大,导致离子峰值的漂移越大.离子在电场起伏下的数值模拟结果与实验中观测到的离子峰值漂移规律一致.     

基于多光子电离的氨/醇混合团簇的飞行时间质谱研究

用多光子电离技术结合飞行时间质谱仪对氨/醇混合团簇进行了研究。在脉冲激光波长为355nm条件下观测到团簇离子。主要的电离产物为质子化的（ROH）n（NH3）mH＋（n=1~6,m=0~4）混合团簇离子,且各个序列的离子强度随m的增大而减小。经分析,氨与醇混合团簇电离后团簇离子发生内部质子化转移反应是形成质子化团簇离子的主要原因。比较分析质谱图可知,当团簇离子比较小的时候二元团簇解离以失去醇类分子为主,随着团簇离子的增大,解离由失去醇分子为主逐渐变为失去氨分子为主。     

醇/水混合团簇的多光子电离质谱及从头算研究

利用多光子电离技术和飞行时间质谱仪实验研究了醇/水混合团簇的光电离质谱。在脉冲激光波长为355nm条件下,观测到以质子化(ROH)n(H2O)H+ 混合团簇离子和(ROH)nH+团簇离子为主的电离产物。醇水混合团簇电离后团簇离子发生内部质子化转移反应是形成质子化团簇离子的主要原因。应用量化计算,构造了质量数较小的几个团簇离子的可能的空间几何构型,发现二元团簇离子(CH3OH)n(H2O)H+是以(CH3OH)H+作为内核离子,再通过氢键与其它分子组合而构成团簇离子。     

导数荧光法研究异丙醇-水配合物的团簇性质

实验获得了异丙醇-水配合物的激发光谱和发射光谱,分析了其荧光发射机理,并用波长为220和232 nm的紫外光激发不同体积百分比的配合溶液得到了荧光光谱,在FFT低通滤波和平滑处理基础上运用导数荧光分析法对其进行优化,进而研究了异丙醇-水配合物的分子团簇性质。结果表明,配合物中异丙醇分子与水分子在H键作用下,以不同方式结合可以形成7种能发荧光的团簇分子,其发射荧光的中心波长分别为277、284、293、309、328、345和362 nm,并根据相对峰位强度得到了各团簇分子数量随溶液浓度变化的规律。     

硅离子簇的理论研究

本文采用ＭＮＤＯ方法研究了Ｓｉｎ，Ｓｉｎ＋和Ｓｉｎ２＋（ｎ＝２—６）簇的原子结构，得到了一系列稳定的簇结构，并确定出每一类簇所对应的最佳稳定结构．从中发现，无论Ｓｉｎ，Ｓｉｎ＋还是Ｓｉｎ２＋簇，都存在共同的“幻数’，即４，５，６，然而，Ｓｉｎ，Ｓｉｎ＋和Ｓｉｎ２＋对应的稳定结构一般是各不相同的．本文的结构说明，以往人们单纯从中性Ｓｉｎ簇的研究去推断并解释Ｓｉｎ离子族的结构和性质是不恰当的，荷电将改变原子簇的构型．文中还指出了几个以前没有发现的稳定构型．     

飞秒强激光脉冲与氢团簇相互作用产生的最大质子能量与团簇尺寸的相关性

报道了飞秒强激光脉冲(60 fs,790 nm,2×1016W/cm2)与纳米尺寸的氢团簇(半径rc约为1~3 nm)相互作用,产生的最大质子能量Emax对于团簇半径rc相关性的实验研究结果。从激光-氢团簇相互作用产生的质子的飞行时间谱测量以及团簇尺寸的瑞利散射诊断结果,得到Emax与r2c成线性正比关系,比例系数为0.75,与报道的理论模拟结果一致,表明氢团簇发生纯库仑爆炸。实验结果同时提示,进一步的理论模拟应考虑气体喷流中团簇的尺寸分布。     

紫外激光多光子电离下甲醇团簇中的反应

应用Nd：YAG脉冲激光器输出的355nm紫外激光实现了对甲醇的多光子电离,通过质谱技术观测到了两个质子化圃簇离子系列：（CH3OH）nH^＋（n=1—15）和（CH3OH）n（H2O）H^＋（n=7—15）,结合在HF／STO-3G和B3LYP／6—31G＋＋水平上的从头计算对其反应通道做了分析,发现其产生经过了团簇内部的质子转移反应。且质子主要来自于羟基上的氢离子。并分析了（CH3OH）nH^＋系列的结构,给出了幻数团簇（CH3OH）3H^＋的构型。同时对（CH3OH）n（H2O）H^＋系列只在n≥7时出现做了相应的解释。     

氢火焰离子化检测系统设计

设计了基于氢火焰离子化检测方法的有机物检测系统。介绍了系统的工作原理,并基于此优化了系统的结构设计;根据系统的反应条件,设计了系统的控制电路;针对系统检测信号微弱、动态范围广的特点,使用跨阻放大的方法设计了量程可切换的电流检测电路,实现了大范围的微电流检测。使用甲烷标准气体测定了系统性能,实验结果表明:标准样品重复性测量相对标准偏差均小于2%,线性相关系数大于0.99。     

Formation of Zn- and O- vacancy clusters in ZnO through deuterium annealing

Open volume defects, clearly distinguishable from the isolated Zn-vacancy are observed in hydrothermally grown ZnO after exposure to deuterium gas at elevated temperatures. From a combination of secondary ion mass spectrometry (SIMS), positron annihilation spectroscopy (PAS) and density functional theory (DFT) calculations it is found that as a result of this treatment vacancy clusters consisting of minimum one Zn- and one O-vacancy are formed, in contrast to introduction of isolated O-vacancies. A scenario for the cluster formation is proposed, where Zn- and O-vacancies originate from the bulk of the sample and the sample surface, respectively. A fraction of the vacancy clusters are decorated by Li and/or H and may therefore be indirectly observed by SIMS. The peak in Li-concentration at about 100 nm below the sample surface, as observed by SIMS is in good correspondence with the PAS-results.     

Experimental and theoretical study of semi-active friction tendons

For purposes of mitigating vibrations, a Semi-Active Friction Tendon (SAFT), which consists of a semi-active friction damper and an auxiliary spring that are linked to the structure by a cable, is studied experimentally, numerically and analytically. Two semi-active control laws are implemented, one is based on velocity-feedback (denoted as SQDCL) and the other is based on force-feedback (denoted as SPCL); the passive control case is also studied for comparison. From the assessment of system displacement and hysteretic behaviour of SAFTs two main conclusions are drawn. First, the effectiveness of the optimized passive-control case can always be improved by using semi-active control with any of the studied control laws. Second, the SPCL is more effective for large displacements, while the SQDCL is more advantageous for very small displacements. Moreover, closed-form expressions for the dissipated energy are derived for the three cases under consideration. These expressions can be used in preliminary design of SAFTs to compare with other alternatives, to decide between passive and semi-active control, and to choose the more suitable control law.     

InGaAsP多量子阱双稳态激光器的实验及理论研究

从实验和理论上研究了InGaAsP多量子阱（Multi-Quantum-Well，MQW）双区共腔（Common Cavity Tandem Section，CCTS）结构半导体激光器的吸收区偏置状态对双稳态特性的影响。实验结果表明:随着可饱和吸收区上的负偏置电压的增大，激光器P-I曲线中双稳态特性更加明显，V-I曲线有负微分电阻，当偏压加至-3 V时，回滞曲线环宽度增加至13.5 mA，开关比达到21:1。理论分析表明，利用吸收区的高负偏置态和短载流子逃逸时间能获得更好的双稳态特性。最大107:1的开关比也说明双区共腔激光器能在两稳态之间实现非常明确的转换。     

氢脉泽中四极磁态选择器的设计及其应用

氢脉泽是一种中、长期稳定度最高的原子频率标准.其中原子磁态选择器的改进设计可以改善氢脉泽的工作参数及其体积与重量,从而改进氢脉泽的品质与工作寿命等,同时也可以改进氢脉泽的长期性能,并给出了磁态选择器的设计与实验结果.     

Synthesis and characterisation of nanometre-sized CdS clusters in chitosan film

A novel process using chitosan containing ligand groups as a medium for forming CdS clusters in chitosan films by an ion co-ordinate method has been investigated. The CdS clusters in the chitosan have been identified by X-ray diffraction and by their infrared, ultraviolet and visible absorption spectra and shown to possess high stability with a specific structure. Notable quantum size effects have been shown through their absorption spectra. By changing the reaction conditions, the wavelength edge of the absorption can be blue-shifted from 470 to 375 nm.     

Experimental and theoretical study of the thermoelectric properties of copper selenide

The temperature dependences of the specific heat, thermal conductivity, coefficient of thermal expansion (CTE), and transport coefficients (electrical conductivity and thermoelectric power) of copper selenide are experimentally and theoretically investigated in the temperature range of 300–873 K. The calculation results correlate with the experimental data up to a temperature of ~773 K. The maximum thermoelectric figure of merit of nanostructured copper selenide is ZT ~ 1.8. The correlation dependence between ZT and the thermal conductivity within the entire temperature range under consideration is shown.