1,2-环己二酮基态光解离反应的理论研究

通过密度泛函理论计算研究了1, 2-环己二酮(α-CHD)基态光解离反应的势能面. 通过IRC方法确定了5个主要的反应通道, 相应的产物分别为P₁(c-C₅H₈O+CO), P₂(2C₂H₄+2CO), P₃(CH₂CHCH₂CH₂CHO+CO), P₄(2CH₂CO+C₂H₄)和P₅(CH₃CHCO+CH₂CHCHO). 获得了反应过程中反应物、产物、中间体和过渡态的结构参数. 详细阐述了这些通道的反应过程, 分析了其反应机理, 总结出最优的反应路径为α-CHD→c-C₅H₈O+CO. 理论分析与实验结果相符. 获得的结果为进一步进行与1, 2-环己二酮相关的研究提供有价值的信息.     

钚氧化物中氢行为的第一性原理研究

通过第一性原理计算和原子级热力学方法，系统研究H、H₂在PuO₂和α-Pu₂O₃中的吸附、扩散和溶解行为.研究发现：氢的上述行为均是吸热过程，但在α-Pu₂O₃与PuO₂中有显著不同：在α-Pu₂O₃中H可自发聚合成H₂，但在PuO₂中H难再聚合；在α-Pu₂O₃中H、H₂均能扩散，通常H会聚合成H₂再扩散，在PuO₂中H₂解离后才能扩散，且PuO₂中H沿高势能面的扩散比α-Pu₂O₃中H₂扩散更容易；在氢压、温度驱动下，氢在α-Pu₂O₃中存在H₂溶解到H+H₂混合溶解机制的转变，平衡气压P_H2远小于H在PuO₂中溶解的情况.基于此，给出PuO₂和α-Pu₂O₃中氢行为的微观图像和PuO₂的阻氢微观机制：PuO₂表面限制H₂解离、渗透，PuO₂块体限制H的溶解，但不阻止H扩散.结合钚氧化层表面氢行为研究获得了钚氢化孕育期的微观机制，为孕育期全过程理论建模提供依据.     

IrB和IrB$lt;sub$gt;2$lt;/sub$gt;力学性质的第一性原理计算

采用平面波赝势密度泛函理论对0–100 GPa静水压下P₁ -IrB（空间群Pnma）和P₅ -IrB₂（空间群Pmmn）结构的平衡态晶格常数、弹性常数等性质进行了研究. 研究结果表明,P₁ -IrB不可压缩性随着压强的增加而增强;P₅ -IrB₂ 结构在0–100 GPa范围内弹性常数、体弹模量、剪切模量均呈现出有规律的变化,当所加压强为50 GPa时,杨氏模量和在b方向的晶格常数发生异常变化. 对零压下P₁ -IrB和P₅ -IrB₂ 的电子结构的研究发现,二者均没有一个明显的带隙,主要原因为Ir原子和B原子间的共价作用. 从P₁ -IrB和P₅ -IrB₂的能带结构和态密度图可以发现这两种结构均有金属性. 关键词： 1 -IrB')" href="#">P₁ -IrB 5-IrB₂')" href="#">P₅-IrB₂ 第一性原理 力学性质     

用夸克模型探索π-N相互作用

本文中用夸克模型,Warke近似,并作为补偿,在夸克唯象势中加入中程势(-1)^T+JKre^(-r/a₂),计算了π-N相互作用势,从此势计算了L_2T,2J=S₁₁,S₃₁,P₁₁,P₃₁,P₁₃和P₃₃六种道的相移。在入射π介子动能E_π^k(lab)=0—700MeV范围内,与由实验方法决定的相移进行了比较。 关键词：     

氯气/BHP液滴化学反应流动一维数值模拟

为研究横向均匀液滴发生器的机理,对Cl₂/He气体横向流过BHP液滴场的物理化学行为建立一维化学反应流动模型.其中气流场按不可压缩假设近似为一维均匀流动;发生于液滴内的化学反应由四种物质的反应扩散方程描述;气相中各种物质浓度由对流扩散方程描述.液滴是这些物质的源或汇,两个模型方程通过此源项相联系.对模型方程作数值求解.结果显示,氯气利用率、单态氧产率及效率与文献所提供的实验结果较为接近,反映了所建模型具备模拟混合气体与BHP液滴反应的基本能力.     

TiSi2薄膜形成中扩散标记的研究

用Xe离子注入作扩散标记,确定了TiSi₂薄膜形成过程中主要扩散元素是Si。应用Kidson和Tu推导的方程根据试验结果计算了600℃退火TiSi₂形成中Si和Ti的扩散系数。 关键词：     

非晶合金Pd80Si20晶化过程中的亚稳相

利用电子显微镜中的倾转晶体法确定了三个晶化相。亚稳相P₁具有简单正交点阵,点阵常数a=0.46,b=1.37,c=1.69nm,可能的空间群为P_nmm:或P_(nm21)。P₁相可用来解释Masumoto等人及Duhaj等人的电子衍射图。另一亚稳相F具有面心正交点阵,其a,b值与P₁相同,c=1.46nm。高温晶化相P₂具有简单正交点阵,点阵常数a=0.3 关键词：     

强磁场下顺磁掺杂离子的光谱扩散

采用一种简明的解析方法从纯粹频域的角度讨论强磁场下顺磁离子掺杂体系的光谱扩散过程。一般说来光谱扩散遵循[1-exp(-WT_w)]^x的形式,W是跳变速率,T_w为等待时间。在不存在冷冻核时,对于频域和时域x分别为1/2和1。考虑到冷冻核效应,光谱扩散的速率将近似地以因子(ω_eff/ω₀)²减慢,这里ω₀是描述冷冻核的特征频率。当冷冻核充分大时,频域和时域的光谱扩散的行为趋于一致x≈0.22。     

磁场对液态铝和固态铁界面微观组织的影响

研究了直流磁场、交流磁场对液态铝和固态铁界面微观组织的影响，采用金相显微镜、电子探针和x射线衍射等方法对其扩散层内生成物进行了分析.结果表明，在直流磁场和交流磁场作用下，固态铁界面内形成的扩散层厚度均比无磁场时小；在交流磁场作用下，液态铝和固态铁的界面变得凹凸不平；在垂直于磁场方向上，直流磁场抑制了铝原子和铁原子之间的扩散，交流磁场则促进了扩散；无磁场时固态铁内扩散层中生成的金属间化合物由FeAl₃和Fe₂Al₅组成，直流磁场条件下只有Fe₂Al_{5生成，交流磁场作用下由Fe2Al5和Fe4Al13组成. 关键词： 磁场 铝 铁 金属间化合物 扩散}     

Al2O3单晶三明治结构的高温热激发电流

以Al₂O₃单晶和具有三明治结构的Al₂O₃单晶-Bi₂O₃-Al₂O₃单晶试样为研究对象,测量了在室温到750℃之间升温过程和降温过程中这两种试样的热激发电流,仅在三明治结构试样中检测到了热激发电流.随测量过程中升温速率的增大,降温过程中的热激发电流逐渐减小.认为热激发电流是由缺陷离子的扩散所引起,通过扩散活化能的计算发现有两种缺 关键词： 热激发电流 缺陷 扩散     

Mixing of Pseudo-Goldstone Bosons and Effects on HERA High-Q2 Events

We study the mixing of pseudo-Goldstone bosons predicted by technicolor theory and the effects on HERA high-Q² events. We find that: (a) there eyist two F = 0 scalar leptoquarks P₃′ with m(P₃′) = 200 GeV and P₃⁰ with m(₃⁰) =225 GeV for β₁ = β₂ = 0.4; (b) the P₃′ and P₃⁰ can contribute the required cross section to account for the excesses of NC and CC high-Q² events; (c) the coexistence of P₃′ and P₃⁰ may be responsible for the splitting of averaged mass of the H1 and ZEUS high-Q² neutral current events.     

超冷铯分子0u+(6P3/2)长程态的高灵敏光缔合光谱研究

利用发展的调制俘获损耗荧光光谱技术实验测量了超冷铯分子0_u⁺(6P_3/2)长程态的高灵敏光缔合光谱. 光谱探测范围较国际已有报道扩大了60 cm^-1, 观察到25个长程区域新的振动能级. 通过LeRoy-Bernstein公式对振动束缚能数据进行拟合, 获得了超冷铯分子0_u⁺(6P_3/2)态的长程系数C₃ 为16.103±0.010. 构建了超冷铯分子0_u⁺(6P_3/2)态长程区域的势能曲线.     

Investigation in thorium phosphate by NMR II-phosphorus dipolar networks

With through space and through bond experiments in two-dimensional NMR we analyze the transformation from the thorium phosphate-hydrogen phosphate hydrate (TPHPH) to the β form of the thorium phosphate diphosphate (β-TPD) in relation with the phosphorus networks. These techniques are complementary: the through space coupling gives an insight on the dipolar phosphorus networks while the through bond coupling is particularly efficient in the detection of the P₂O₇ groups. With these experiments we show that in a first step, by heating the precursor TPHPH above 250 °C, it transforms into an form of TPD. This transformation is due to the complete condensation of hydrogen phosphate groups HPO₄ into P₂O₇ entities. By heating -TPD above 950 °C it transforms into its well-known β form. The form is characterized by a hygroscopic behavior: some water molecules are present near the P₂O₇ groups that makes non-equivalent their phosphorus nuclei. PO₄ dipolar networks are always present in the form. The main effect of these PO₄ and P₂O₇ units is to give the system a channel structure and the water enters in them.     

49S里德堡态的射频双光子光谱

在室温铯原子蒸气池中, 由铯原子基态、激发态和里德堡态构建了阶梯型三能级系统, 研究了里德堡原子阶梯型三能级系统的电磁感应透明(EIT). 在实现电磁感应透明的基础上, 利用16.9 GHz的射频电场耦合相邻的原子里德堡态, 实现49S_1/2→47D_3/2的双光子跃迁, 测量了里德堡原子的射频双光子光谱, 观察到了电磁感应透明光谱的分裂, 进一步研究了电场强度对射频双光子光谱的影响. 利用里德堡原子的EIT效应可实现对射频电场幅值和极化的精密测量, 具有潜在的应用前景.     

Kinetic Phase Transition in A2 ＋ 2B2 → 2B2A Reaction System with Particle Diffusion

A lattice gas model is presented for the A2 ＋2B2 → 2B2A reaction system with particle diffusion in two dimensions. In the model, B2 dissociates in the random dimer-filling mechanism and A2 dissociates in the end-on dimer filling mechanism. A reactive window appears and the system exhibits a continuous phase transition from a reactive state to a ＂B ＋ vacancy＂ covered state with infinitely many absorbing states. When the diffusion of particle B is considered, there are only two absorbing states. It is found that the critical behavior of the continuous phase transition changes from the directed percolation （DP） class to the pair contact process with diffusion （PCPD） class.     

Rydberg原子nS1/2→(n+1)S1/2双光子激发EIT-AT光谱

主要研究了热原子蒸气池中铯Rydberg原子nS_1/2→(n+1)S_1/2微波耦合的双光子光谱.铯原子基态(6S_1/2)、第一激发态(6P_3/2)、Rydberg态(69S_1/2)形成阶梯型三能级系统,弱探测光作用于基态到激发态6S_1/2→6P_3/2的跃迁,强耦合光则作用于6P_3/2→69S_1/2的Rydberg跃迁形成电磁感应透明(EIT)效应,实现对Rydberg原子的光学探测.频率fMW=11.735 GHz的微波场耦合69S_1/2→70S_1/2的Rydberg跃迁,形成微波双光子光谱.利用EIT-AT分裂光谱研究微波电场强度对双光子光谱的影响.研究表明:在强微波场作用时,EIT-AT分裂与微波场功率成正比,而弱微波场时的EIT-AT分裂与微波场功率成非线性依赖关系,理论计算与实验测量结果相一致.本文的研究对微波电场的精密测量具有一定的指导意义.     

Rydberg原子nS1/2→(n+1)S1/2双光子激发EIT-AT光谱

主要研究了热原子蒸气池中铯Rydberg原子nS_1/2→(n+1)S_1/2微波耦合的双光子光谱.铯原子基态(6S_1/2)、第一激发态(6P_3/2)、Rydberg态(69S_1/2)形成阶梯型三能级系统,弱探测光作用于基态到激发态6S_1/2→6P_3/2的跃迁,强耦合光则作用于6P_3/2→69S_1/2的Rydberg跃迁形成电磁感应透明(EIT)效应,实现对Rydberg原子的光学探测.频率fMW=11.735 GHz的微波场耦合69S_1/2→70S_1/2的Rydberg跃迁,形成微波双光子光谱.利用EIT-AT分裂光谱研究微波电场强度对双光子光谱的影响.研究表明:在强微波场作用时,EIT-AT分裂与微波场功率成正比,而弱微波场时的EIT-AT分裂与微波场功率成非线性依赖关系,理论计算与实验测量结果相一致.本文的研究对微波电场的精密测量具有一定的指导意义.     

Ionic diffusion and local hopping in copper chalcohalide glasses measured using Cu tracer and I-Mössbauer spectroscopy

For the first time, ⁶⁴Cu tracer measurements of ionic diffusion were performed for several copper-rich glass compositions in the CuI---As₂Se₃, CuI---SbI₃---As₂Se₃, CuI---PbI₂---As₂Se₃, CuI---PbI₂---SbI₃---As₂Se₃ and Cu₂Se---As₂Se₃ systems. In accordance with previous a.c. impedance results and Wagner d.c. polarization measurements, it was found that pure Cu⁺ ion-conducting glasses (50CuI---17PbI₂---33As₂Se₃ and 50CuI---20PbI₂---10SbI₃---20As₂Se₃) exhibit the highest copper tracer diffusion coefficients, D_Cu, and the lowest diffusion activation energies. The values of D_Cu at room temperature are higher by 4.5–5.5 orders of magnitude than those in an As₂Se₃ glass. The Haven ratio, H_R, is found to be 0.52–0.61 (ternary glass) and 0.93–1.00 (quaternary glass). Short-range diffusional displacements of the iodide ions induced by the hopping Cu⁺ ions are also detected in the CuI---PbI₂---SbI₃---As₂Se₃ glassy system using ¹²⁹I-Mössbauer spectroscopy in the temperature range of 4.2 to 305 K. The activation energy of local hopping, E_h ≈ 0.31 eV, is very similar to that of bulk ionic conductivity (0.37 eV) and copper diffusion (≈ 0.33 eV). In contrast to CuI-based vitreous alloys, 50Cu₂Se---50As₂Se₃ glass exhibits D_Cu that are two to five orders of magnitude lower, and the copper ion transport number, t_Cu⁺, is between 10⁻³ and 10⁻⁴ in the temperature range 140–170 °C.     

Boron diffusion in bcc-Fe studied by first-principles calculations

The diffusion mechanism of boron in bcc-Fe has been studied by first-principles calculations. The diffusion coefficients of the interstitial mechanism, the B–monovacancy complex mechanism, and the B–divacancy complex mechanism have been calculated. The calculated diffusion coefficient of the interstitial mechanism is D_0= 1.05 ×10~(-7)exp(-0.75 e V/k T) m~2· s~(-1), while the diffusion coefficients of the B–monovacancy and the B–divacancy complex mechanisms are D_1= 1.22 × 10~(-6)f1exp(-2.27 e V/k T) m~2· s~(-1)and D_2≈ 8.36 × 10~(-6)exp(-4.81 e V/k T) m~2· s~(-1), respectively. The results indicate that the dominant diffusion mechanism in bcc-Fe is the interstitial mechanism through an octahedral interstitial site instead of the complex mechanism. The calculated diffusion coefficient is in accordance with the reported experiment results measured in Fe–3%Si–B alloy(bcc structure). Since the non-equilibrium segregation of boron is based on the diffusion of the complexes as suggested by the theory, our calculation reasonably explains why the non-equilibrium segregation of boron is not observed in bcc-Fe in experiments.