Cu(100)表面上H2/D2散射的六维态-态量子动力学研究：位点平均模型的有效性

基于由optPBE-vdW密度泛函计算的数千个数据点拟合得到的精确的神经网络势能面,本文采用含时波包方法对H₂/D₂在刚性Cu(100)表面上的态-态散射进行了六维量子动力学计算. 与以往的理论和实验比较了H₂和D₂在Cu(100)中的振转(非)弹性散射的结果. 特别是通过将六维的(非)弹性散射几率与从十五个位点加权平均四维几率的结果比较,测试了在该体系中位点平均近似模型的有效性. 具体来说,位点平均模型很好地重现了振动弹性散射几率,尽管对于高能下的振动非弹性散射结果没那么好. 结果说明在未来研究重双原子或多原子分子从金属表面的态-态散射动力学时,可以使用位点平均模型来降低全维计算过高的成本.     

物质动态结构的非弹性散射研究

在静态结构的基础上，考虑原子的振动，分子键的振动、转动和振－振运动的结构称为动态结构，它是用非弹性散射方法来测定的。本文评述研究动态结构的实验方法：中子非弹性散射，非弹性X射线散射、核非弹性散射和Raman散射以及红外吸收谱。简单介绍了声子散射理论基础，继后，分三节描述了用这些方法来研究动态结构的若干结果。1）结晶物质，包括晶内，表面和界面，高纯近完整晶体中杂质引起的，多晶中、薄膜和纳米晶体中的点阵动力学研究；2）非晶物质，包括非晶固体，高聚合物，生物大分子，准晶和液体的动态结构研究；3）高温超导体的点阵动力学研究，文末给出了小结和最后评论。     

超冷(36D5/2+6S1/2)里德伯分子的制备及其电偶极矩的测量

里德伯-基态分子由一个里德伯原子和一个基态原子组成,束缚机制是里德伯电子与基态原子的低能电子散射相互作用.理论上,通过低能电子散射Fermi赝势模型,数值计算了铯(36D_5/2+6S_1/2)里德伯-基态分子的绝热势能曲线,提取了里德伯分子的束缚能和平衡核间距等光谱参数.实验上,利用双光子光缔合技术成功制备了散射三重态(^T∑,Triplet)和散射单重态-三重态混合(^S,T∑,Mixed)形成的里德伯-基态分子,获得了里德伯分子的光缔合光谱,测量的势阱深度与理论计算结果相吻合.另外,以散射三重态为例,分析了里德伯分子的光缔合光谱在外加电场中的展宽现象,获得其平均永久电偶极矩|d|为(12.10±1.65) Debye ((4.76±0.65)ea₀),与理论计算结果保持一致.该研究为实验上制备D态里德伯-基态分子提供了可行的实验方案,对理解里德伯分子的光谱特性具有重要意义.     

高里德堡态氢原子与氦原子散射的高分辨研究

利用了氢原子飞渡时间谱实验方法对处于高n主量子数里德堡态的氢原子与氦原子的分子束散射过程进行了高分辨研究.测量了H(n)+He→H(n′)+He散射过程的散射微分截面.实验结果表明,产物主要分布在前向散射方向,在侧向也有一定的分布.在前向和侧向存在大量的振荡结构.同时详细的研究也表明,在上述的散射过程中往前散射的方向上,氢原子里德堡态主量子数n的变化并不是很大.实验结果得到了为理论上精确研究高n主量子数里德堡态的氢原子与氦原子的散射动力学的一套精细的实验数据.     

物质动态结构的非弹性散射研究

在静态结构的基础上 ,考虑原子的振动 ,分子键的振动、转动和振—转运动的结构称为动态结构 ,它是用非弹性散射方法来测定的。本文评述研究动态结构的实验方法 :中子非弹性散射、非弹性X射线散射、核非弹性散射和Raman散射以及红外吸收谱。简单介绍了声子散射理论基础。继后 ,分三节描述了用这些方法来研究动态结构的若干结果。 1 )结晶物质 ,包括晶内、表面和界面、高纯近完整晶体中杂质引起的、多晶中、薄膜和纳米晶体中的点阵动力学研究 ;2 )非晶物质 ,包括非晶固体、高聚合物、生物大分子、准晶和液体的动态结构研究 ;3 )高温超导体的点阵动力学研究。文末给出了小结和最后评论。     

F+H2→HF+H反应的全量子态分辨的散射动力学研究

利用高灵敏度的氢原子里德堡飞渡时间谱方法研究了 F H_2→HF H 反应碰撞能在5.02kJ/mol 下的交叉分子束反应态态散射动力学.所有在时间飞渡谱中被观测到的谱峰可以归属为 HF 产物的振转态结构.还观测到了明显的 HF(v’=3)前向散射,以及少许的 HF(v’=2)前向散射.     

三体散射的动力学

研究非线性相互作用的一维三原子集团之间的散射动力学,揭示随着系统能量的增加依次出现的混沌散射、非完全弹性散射、完全弹性散射现象,研究内部动力学属性,特别是混沌运动行为与散射行为之间的关系,解释混沌散射不可预测性的机制.     

激光场中电子与氢原子的散射：Ⅱ.低频近似下的计算

本文在多重散射理论的框架下,研究了低频激光场中电子与氢原子的散射。计算了激光场中电子与基态氢原子弹性散射的微分截面,讨论了微分截面随光子数、散射角以及入射电子能量的变化规律,并与别人的结果作了比较。     

~6Li超冷费米气体宽Feshbach共振散射的动力学演化研究

本文解析研究了~6Li超冷费米气体宽Feshbach共振散射动力学演化过程,将整个散射过程转化为一个单重态和一系列准连续态的散射共振,等效于涉及接触势的散射过程,在原子波包的持续时间内,束缚态中不断地出现原子布居,并将输入的波包非弹性散射到与之耦合的所有通道中。随着相互作用时间的增加,布居数转移幅度越来越大,连续态和束缚态之间的散射概率逐步增加,最终达到碰撞稳态。同时我们定量的计算了在原子散射过程中连续态和束缚态的动力学演化,在散射过程中连续态和束缚态的总概率守恒,连续态和束缚态之间布局数交换发生在散射共振前后的数十纳秒时间内。     

分子（H2,D2）与固体表面散射的理论研究

在含时量子计算方法的基础，利用量子散射中的角动量耦合理论等，导出了分子与固体表面非弹性散射的计算公式，对分子（Ｈ２，Ｄ２）与粗糙固体表面在较低能量下的非弹性散射做了计算，得出了模型势下的散射规律。     

State-to-state dynamics of high-n Rydberg H-atom scattering with D2

Full quantum-state resolved scattering of a highly excited Rydberg H atom with D2 has been carried out using the Rydberg H-atom time-of-flight method. A detailed analysis of the experimental results shows that both inelastic and reactive scatterings are significant in the Hn-D2 collisions, and nuclear spin is conserved in the inelastic scattering process. The differential cross sections for the Hn-D2 reaction measured in this work are then compared with the results for the H+ reaction with D2 in an ion beam scattering experiment. The remarkable agreement between the two experiments suggests that the Fermi independent-collider model is valid even at the full quantum state-to-state scattering level, providing a promising tool for investigating the state-to-state dynamics of certain elementary ion-molecule reactions.     

F+H2化学反应中的Feshbach共振之研究

化学反应共振态研究是化学动力学研究的重要前沿课题,对于理解基元化学反应的机理有重要的意义.本文中介绍了最近在这一研究方向的重大进展.通过对F＋H2化学反应的全量子态分辨的分子束反应散射实验研究,观测到了F＋H2中反应中明显的反应共振现象.通过高精度的全量子散射动力学研究,发现这一共振现象是由两个Feshbach共振态所引起的,而且这两个Feshbach共振态之间在前向散射有明显的量子干涉效应.这项研究工作使得我们对这一重要基元反应中的化学反应共振态研究向前迈进了一大步。     

A quantum wavepacket study of three-dimensional Ne—H+ 2 scattering

The state-to-state and state-to-all reaction probabilities have been calculated for three-dimensional reactive and inelastic scattering of Ne + H⁺ ₂ (v = 0, j = 0, 1, 2) at zero total angular momentum. The time-dependent Schrödinger equation is solved by means of Fourier grid and discrete variable representation techniques. The inelastic and reactive scattering probabilities for a broad range of energies are calculated. Although the system has an open reactive channel, the results show that a high fraction of the flux is reflected back due to endoergicity and potential barriers leading to inelastic scattering.     

Anomalous quasielastic electron scattering from single H2, D2, and HD molecules at large momentum transfer: indications of nuclear spin effects

Quasielectron electron scattering from gaseous H2, D2, a 50:50 mixture of H2 and D2, and HD is investigated with 2.25 keV impact energy and a momentum transfer variant Planck's over 2piq of 19.7 a.u. The energy transfer is less than the dissociation energy. The spectral positions of the H and D recoil peaks agree with Rutherford scattering theory. Surprisingly, in the spectrum of the 50:50 H2-D2 mixture, the integrated intensity of the H peak is 31%+/-4% lower (as compared to that of D) than predicted by Rutherford scattering, despite equal screening of nuclear charges by the electrons. In contrast, the ratio of scattering intensities from H and D in HD agrees with the predictions of Rutherford scattering. Comparison is made with neutron Compton scattering results from the same systems, but at higher energy transfers causing bond breaking. Possible theoretical explanations are outlined.     

Effect of a single quantum rotational excitation on state-to-state dynamics of the O(1D)+H2-->OH+H reaction

Crossed molecular beams scattering experiments on the O(1D)+H2 reaction have been carried out in order to study the effect of the reagent (H2) rotational excitation on the detailed dynamics of this benchmark insertion reation. Experimental results indicate that a single quantum rotational excitation of H2 has a significant impact on the product state distributions at the forward and backward scattering directions, while very little effect has been found in the sideway scattering direction. No clear patterns of this effect are found in the OH-product state distributions, indicating that the single quantum excitation on the dynamics is rather complicated.     

用电子散射研究丰质子核的质子晕结构

理论和实验结果都表明¹⁷F的第一激发态有质子晕存在.用相对论平均场理论和Eikonal近似研究了质子晕核¹⁷F的第一激发态的电子弹性散射过程. 计算了¹⁷F的第一激发态的电荷形状因子,并与¹⁶O和¹⁹F的结果进行了对比和讨论.结果显示质子晕的存在会使中等转移动量的电荷形状因子产生明显的变化,并且使低转移动量的电荷形状因子趋于降低.这说明电子散射对质子晕的存在是非常敏感的,表明可以用电子散射对奇特核的质子晕结构进行更精细的研究.     

Cd2SnO4薄膜光致发光某些性质的研究

本文研究了Cd2SnO4薄膜光致发光的某些性质.Cd2SnO4膜是利用Cd-Sn合金靶在Ar+O2气氛中反应溅射而成的.实验研究表明,Cd2SnO4膜的发光峰值随着氧浓度的增加移向长波方向.这是因为氧浓度的增加,减少了膜中的氧空位,导致了导带中电子浓度的减小,致使Burstein-Moss效应和电子散射作用相对减弱,从而改变了带隙宽度.     

Separation of changes in light scattering and chromophore concentrations during cortical spreading depression in rats

We used near-infrared spectroscopy to separate tissue scattering changes from changes in cerebral oxyhemoglobin and deoxyhemoglobin and the redox state of cytochrome- c -oxidase. A separate term of the transport scattering coefficient (micro(s)(?)) was included in a modified Lambert-Beer equation. It is shown by diffusion equation analysis that there is a simple relationship between the differential path-length factor (D(a)) and its scattering equivalent (D(s)) . The method was applied to cortical spreading depression (CSD) data recorded through the skulls of rats. Biphasic changes in micro(s)(?)of +/-0.1mm(-1)were observed during CSD's that spread with a velocity of ~5mm/min . The method proposed has the promise to permit monitoring of scattering changes noninvasively in humans during cortical activation or pathophysiological conditions.     

Scattering of an electromagnetic wave from a planar waveguide structure with a slightly 2D random surface

This paper deals with the scattering of an electromagnetic (EM) wave from a waveguide structure with a slightly rough surface. The waveguide structure is a dielectric film on a planar, perfectly conductive surface, and the top of the film is a two-dimensional (2D) homogeneous Gaussian random surface. The treatment is based on the stochastic functional theory where the random EM field is represented in terms of a Wiener - Hermite functional of the random surface. Numerical calculations show that enhanced backscattering and cross-polarization occur, but that no enhanced satellite peak appears for a 2D random surface, in contrast to the case of a 1D surface. The enhanced backscattering is caused by the interference of two double-scattering processes and is attributed to the existence of guided waves in the scattering structure.     

复杂媒质散射特性的FETI分析

在分析复杂媒质的电磁场散射特性时,引入有限元撕裂对接法,对包含复杂媒质在内的整个计算空间做区域分解,通过合理的代数运算,将一个三维问题转化为二维问题进行求解,减小计算的复杂度.使用Krylov求解器,避免在形成交界面系统方程时,系数矩阵中的求逆运算.两个算例结果表明有限元撕裂对接法在分析复杂媒质散射特性时的正确性和有效性.