氯分子束与InP(100)表面反应散射的角分布研究

采用角分辨分子束散射技术研究了Cl_2与InP(100)表面热反应和激光诱导反应产物的角分布. 对于热反应, 由调制分子束和可转动四极质谱仪测得产物离子InCl~+、InCl_2~+、PCl~+、PCl_2~+和P_4~+的角分布, 都可用cos~(1.5)θ函数报合. 对于紫外(355 nm)激光诱导反应, 由飞行时间质谱法测得主要产物离子的角分布明显地偏离Knudsen定律. 其中In~+, InCl~+和InCl_2~+的角分布可用α·cosθ+(1-α)cos~nθ函数拟合, 其中α和n为拟合参数, 对于不同的产物离子有不同的数值. 由实验测得的脱附粒子的通量和能量在表面法线方向有明显地聚集现象, 可以认为产物从表面上脱附的机理, 除了热脱附之外, 还有非热脱附以及在表面附近脱附粒子的碰撞效应.     

氯分子束与钛表面激光化学反应动力学

本文采用飞行时间质谱技术测定了在紫外(355nm), 可见(560nm)和近代红外(1064nm)脉冲激光作用下, 氯分子束与Ti表面反应产物的质量分布和速度分布。所得结果表明, 不同波长激光诱导反应的主要产物相同, 有Ti, TiCl, TiCl3和TiCl4。在高能量密度的紫外激光作用下, 首次测得具有很高动能的原生Ti+。各种含Ti氯化物的飞行时间谱, 能满意地用单组分或多组分Maxwell-Boltzmann公式拟合和分析。上述激光诱导气-固表面反应的机理主要由氯分子在Ti表面上的解离吸附,吸附态氯原子在表面上生成TiClx(X=1～4)的连串反应以及激光诱导脱附所组成。近红外激光主要引起热脱附, 而紫外激光的作用还原可能有非热脱附过程。     

超声分子束研究激光诱导Cl2和Ta表面反应动态学

本文研究了在三种不同波长的脉冲激光(365 nm, 560 nm和1064 nm)辐照下超声Cl_2分子束与多晶Ta表面的化学反应动态学. 由四极质谱和飞行时间增(TOF)测定了产物的质量分布和速度分布. 该反应的主要产物为TaCl, TaCl_2, TaCl_3及TaCl_4; 它们的TOF谱都可用Maxwell-Boltzmann分布拟合, 所得的平动温度分别在500 K—1500 K范围内. 测定了各种产物相对产率与激光能量密度和入的Cl_2分子平动能的关系. 此外, 对此气-固表面反应的机理进行了讨论。     

角分辨飞行时间法研究紫外激光烧蚀Ta2O5的反应

利用角分辨飞行时间法研究了３５５ｎｍ脉冲激光烧蚀Ｔａ２Ｏ５的反应，由四极质谱测得的煤蚀产物除了Ｏ，Ｔａ，ＴａＯ和ＴａＯ２中性碎片外，在较高激光能量密度时还有Ｏ，Ｔａ，ＴａＯ，ＴａＯ２离子碎片，它们的飞行时间（ＴＯＦ）谱可以用于级分带质心速度的Ｍａｘｗｅｌｌ－Ｂｏｌｚｔｍａｎｎ分布函数较好地拟合，原生离子碎片的平均动能与激光能量密度无关，烧蚀产物原生离子和中性粒子的角分布可以分别用ａｃｏｓ＾ｎθ（ｎ     

n-C_3H_7I和i-C_3H_7I的激光裂解

Wilson等人曾研究过碘代烷在266nm的激光光解RI→R+I＊(~2P_(1/2))(1)RI→R+I(~2P_(3/2))(2)由于他们所用的光解产物谱仪不能改变产物的检测方向,因而对C_2H_5I,n-C_3H_7I和i-C_3H_7I的光解通道(1)和(2)在飞行时间(TOF)谱上的分离没有成功。我们用束源可转动的分子束激光裂解产物谱仪(飞行距离531mm)研究了CH_3I和C_2H_5I在248nm的激光裂解后,又分别对n-C_3H_7I和i-C_3H_7I进行研究,并实现了I＊(~2P_(1/2))和I(~2P_(3/2))光解通道在TOF谱上的分离,测得光解通道比见表1。     

355 nm激光烧蚀LiMn2O4反应产物的飞行时间质谱

采用角分辨飞行时间质谱法研究了355 nm脉冲激光烧蚀LiMn2O4的反应. 在较低激光能量密度(0.8 J·cm^-2)测得的离子和中性烧蚀产物主要有Li, O, LiO, LiO₂ , Mn, Li₂, Li₄, Li₆, LiMn, MnO, MnO₂等. 激光能量密度较大时, 烧蚀产物中的氧化物不仅相对量增加, 而且物种更加丰富. 它们的飞行时间谱可用带质心速度的Maxwell-Boltzmann分布函数拟合. 烧蚀产物Li, LiO, LiO₂ 和 Mn存在能量密度表观阈值, 并且离子产物的阈值比相应的中性产物高. 烧蚀产物中原生离子和中性产物的空间角分布可用cosⁿ θ 或θ cosθ+(1-δ)cosⁿθ拟合. 此外, 对355 nm脉冲激光对LiMn₂O₄的烧蚀机理进行了讨论.     

分子离子双激发解离通道的竞争

建立了三原子分子离予XYZ＋（XY2^＋）解离产生多种离子产物时Eα和Eβ两个解离通道之间竞争的理论模型．实验测量出碎片产物分支比和对两束解离光光强比的依赖关系后,由理论公式对数据进行拟合获得拟合参数,可以计算出两个激发解离通道α和β的激发截面分支比．     

用原子序数连接性指数研究烷基衍生物的标准生成焓

通过对杂原子染色给出每个非氢原子的序数（fi)，它对分子中非氢原子实现 唯一性表征。基于邻接矩阵和fi建立析的连接性指数（^mF），其中^1F对烷烃的其 衍生物具有良好的结构选择性，拟合42种烷基衍生物的标准生成焓（△fHm^θ)与 ^1F的直线与曲线方程为：-△fHm^θ=-131.98+101.76^1F,r=0.9884,-△fHm^θ=- 24.55+27.34^1F^1.75,r=0.9956。相关性明显优于文献报道的研究结果（其r为0. 2930)。     

牛血红蛋白与银纳米粒子相互作用的光谱研究

运用紫外-可见吸收光谱(UV-Vis)、荧光光谱、同步荧光光谱、圆二色光谱(CD)及傅立叶变换红外光谱(FTIR)等手段, 研究牛血红蛋白(Bovine Hemoglobin, 简称BHb)与银纳米粒子的相互作用. 结果表明, BHb能吸附在银纳米粒子的表面, 使其415 nm处的特征等离子体共振吸收峰强度下降, 峰位红移. 随银纳米粒子的浓度增大, BHb分子中Soret带的吸收持续降低, 说明银纳米粒子可能使部分血红素辅基从它们的键腔中脱离出来. Stern-Volmer方程分析表明, 银纳米粒子静态猝灭BHb的内源荧光. 由UV-Vis和荧光光谱的变化, 计算BHb与银纳米粒子的结合常数, 其数量级达到10⁹～10¹⁰. 同步荧光光谱的蓝移说明, 银纳米粒子扰动BHb分子内部的酪氨酸、色氨酸残基所处的微环境, 使之包埋于疏水腔中. 拟合计算远紫外CD数据发现, 银纳米粒子诱导BHb产生轻微的二级结构改变, α-螺旋含量降低. FTIR光谱结果提示, BHb中半胱氨酸残基的硫、羧基氧、酰胺及氨基酸残基中的氮原子与银纳米粒子可能有表面键合作用.     

靶向MPO的磁性纳米粒子的制备与表征

将表面含有大量氨基的树枝状分子聚酰胺-胺与油溶性的氧化铁纳米粒子(IONPs)进行配体交换,制备了水溶性氧化铁纳米粒子,将动脉粥样硬化斑块中髓过氧化物酶(MPO)的靶向分子5-羟色胺(5-HT)接枝到以树枝状分子为载体的体系上,最后得到树枝状分子包覆IONPs纳米粒子-g-PEG-g-5-羟色胺(5-HTPEG-G3.0@IONPs),可以作为一种靶向动脉粥样硬化斑块的核磁造影成像剂.通过测试产物的红外光谱(FTIR),证明合成了5-HT-PEG-G3.0@IONPs纳米粒子.TEM测试结果表明该纳米粒子的的粒径约为10 nm左右,DLS测试结果显示的粒径约为31.0 nm.利用5-HT具有紫外特征吸收峰(276 nm),确定了终产物中5-HT的接枝量为6.19μg/mg.TGA结果表明5-HT-PEG-G3.0@IONPs的氧化铁含量为2 wt%.VSM测试结果表明该产物具有超顺磁性,且饱和磁化强度为1.47 A·m2/kg.     

Molecular Beam Studies on the Laser-Enhanced Surface Reaction of GaAs(100) with Chlorine

A cw supersonic Cl₂ molecular beam coupled with an angle-resolved time-of-flight (TOF) technique has been used to investigate the laser-enhanced surface reaction of GaAs(100) with chlorine. The mass and velocity distributions of the major reaction products under 1064 nm laser irradiation have been measured as a function of laser fluence, detection angle, surface temperature and normal component of the translational energy of the incident chlorine molecules. It has been found that increasing both laser fluence and the translational energy of incident chlorine molecules markedly enhance mis surface reaction. The measured flux angular distributions of major reaction products can be fit satisfactorily with a bi-cosine function. Measurements of the mass and angular distributions of reaction products by a modulated molecular beam mass spectrometry show that the surface temperature effect is obvious for the Cl₂/GaAs(100) “dark” thermal reaction. A direct activated dissociative chemisorption is proposed for the mechanism of Cl₂ chemisorption on the GaAs(100) surface.     

The collimation angle shift of desorbing product N2 in a steady-state N2O+CO reaction on Rh(110)

The angular distribution of desorbing product N2 was studied in N2O decompositions on Rh(110) in the temperature range of 60-700 K. The N2 desorption collimates along 62 degrees -68 degrees off normal toward either the [001] or [001] direction in a transient N2O decomposition below ca. 470 K or in the steady-state N2O+CO reaction above 540 K. In the steady-state reaction at the temperature from ca. 470 to 540 K, however, the collimation angle shifts from 62 degrees to 45 degrees with decreasing surface temperature. This angle shift is ascribed to the steric hindrance by coadsorbed CO because the N2 collimation in transient N2O decomposition at around 65 degrees is recovered in the range of 380-500 K by an abrupt CO pressure drop followed by the decrease in CO coverage. N2O is oriented along the [001] direction before dissociation. A scattering model of the nascent N2 by adsorbed CO is proposed, yielding smaller collimation angles.     

Spatial distributions of desorbing products in basic catalytic processes and surface nano-structures

Reviews of recent progress in angle-resolved measurements of desorbing surface reaction products are discussed. The angular and velocity distributions of desorbing products deliver information about the reaction site as well as the reaction mechanism when the products are repulsively desorbed. These distribution measurements can yield symmetry and orientation information of the reaction site for associative processes whereas, in dissociative desorption, the collimation of fragment desorption is related to the orientation of the intermediate species immediately before dissociation. These different collimations provide information on desorption steps whenever any step becomes rate determining.     

1064nm激光诱导Ge(111)与Cl2反应动力学

采用超声分子束和时间分辨质谱技术研究了1064nm脉冲激光辐照下Ge(111)与Cl₂的反应动力学。实验结果表明,该反应的主要产物为GeCl₂,提高入射氯分子的平动能将增加反应速率。激光能量密度对GeCl₂产率呈指数关系,而对GeCl₂的平动温度影响不大。升高Ge(111)表面温度也能提高反应产率。同时还讨论了近红外激光诱导GeCl₂反应的机理。     

氯原子与丙烷反应的准经典轨线研究

氢原子取代反应为化学反应动力学的研究提供了许多有用的信息,人们对这些轻原子转移反应在理论和实验上都进行了大量研究［１］．最近,一些实验对Ｃｌ原子与烃反应提供了直接信息．Ｓｉｍｐｓｏｎ等［２］利用核抽取的方法测量相关态和散射分布来研究Ｃｌ原子与振动激发态...     

苯热GaP纳米微晶介质中水氧对反应过程的影响

分别以磷和GaCl~3的乙醚溶液、GaCl~3的苯溶液为原料,用苯热合成法制备了GaP纳米微晶。初步探讨了反应过程中介质中的水和氧对生成物的影响,并利用化学键的解离能数据对生成物的稳定性进行了分析。结果表明：介质中的水和氧可以在很大程度上影响反应过程,甚至改变反应进行的方向。     

Correlated angular and quantum state-resolved CO2 scattering dynamics at the gas-liquid interface

Molecular beam scattering dynamics at the gas-liquid interface are investigated for CO2 (E(inc) = 10.6(8) kcal/mol) impinging on liquid perfluoropolyether (PFPE), with quantum state (v, J) populations measured as a function of incident (theta(inc)) and final (theta(scat)) scattering angles. The internal state distributions are well-characterized for both normal and grazing incident angles by a two-component Boltzmann model for trapping desorption (TD) and impulsive scattering (IS) at rotational temperatures T(rot)(TD/IS), where the fractional TD probability for CO2 on the perfluorinated surface is denoted by TD and IS densities (rho) as alpha = rhoTD/(rhoTD + rhoIS). On the basis of an assumed cos(theta(scat)) scattering behavior for the TD flux component, the angular dependence of the IS flux at normal incidence (theta(inc) = 0 degrees) is surprisingly well-modeled by a simple cos(n)(theta(scat)) distribution with n = 1.0 +/- 0.2, while glancing incident angles (theta(inc) = 30 degrees, 45 degrees, and 60 degrees) result in lobular angular IS distributions scattered preferentially in the forward direction. This trend is also corroborated in the TD fraction alpha, which decreases rapidly under non-normal incident conditions as a function of backward versus forward scattering direction. Furthermore, the extent of rotational excitation in the IS channel increases dramatically with increasing angle of incidence, consistent with an increasing rotational torque due to surface roughness at the gas-liquid interface.     

Monte Carlo calculation of angular transmission functions for small angle scattering

We define an angular transmission function η in the center of mass system. The convolution of the differential cross section σ with η yields the signal in the laboratory system. For the case of elastic small angle scattering by spherically symmetric potentials we calculate η by a Monte Carlo method. Random positions are taken in the beam defining collimators, resulting in a trajectory with a deflection angle at the scattering centre. These deflection angles are transformed to the c.m. system with the small angle tranformation formulae. From the distribution we calculate η as a histogram and the central moments of η. The function η depends on the velocity ratio and on the mass ratio of the scattering partners. We store the results in such a way that the central moments can be calculated afterwards for all mass and velocity ratios. By using the central moments the convolution integral can be reduced to a simple weighted sum of σ-values at different scattering angles. The r.m.s. deviations of the central moments scale with N^{$\text{1}\text{2}$}, with N the number of Monte Carlo trajectories. A typical deviation is 1% in the second order moment for N = 2 × 10⁴, increasing slightly with increasing order of the moments. This method of calculation gives a large degree of freedom for optimisation of the collimation geometry. The use of an angular transmission function defined in the center of mass system gives a good insight in the experimental reflection of the physical events. As an example we apply the method to the case of small angle scattering of Ar as a primary beam by Kr as a secondary beam and the inverse configuration of Kr by Ar.