钡准分子共振电离光谱及离化机制研究

本文报道用激光共振电离法获得一个新的钡准分子结构.在染料激光波长扫描范围内观察到钡原子双光子共振跃迁、双光子混合跃迁和钡准分子谱带.我们提出一种用热离子二极管信号特性分析原子和分子里德伯态的离化机制的方法,并以此对钡原子和钡分子的离化通道进行讨论.     

XeCl准分子激光的超精细光谱结构

本文通过振动-旋转耦合的旋转谱线计算,解释了XeCl准分子激光的超精细光谱结构.计算结果与实验很好地符合.     

锶Sr,钡Ba和镭Ra的单光子电四极矩光谱跃迁的理论研究

用带有Ｂｒｅｉｔ和ＱＥＤ修正的全相对论多组态Ｄｉｒａｃ－Ｆｃｃｋ平均能级（ＭＣＤＦ－ＡＬ）模型,计算了碱土金属Ｓｒ、钡Ｂａ和镭Ｒａ的单光子电四极矩＾１Ｄ－＾１Ｓ跃迁的光谱能量间隔,最大跃迁几率和振子强度。计算中考虑了重要的相对论效应、电子关联效应和核的有限体积效应,所得的结果与国外早期发表的结果进行了比较,此外还首次从理论上预言了镭Ｒａ的单光子电四极矩＾１Ｄ－１Ｓ光谱跃迁。     

单电荷态钡离子超精细结构光谱

采用共线快离子束激光光谱学方法研究了钡离子亚稳态5d²D_3/2和激发态6p²P_3/2的超精细结构,并定出了相应的超精细结构常数. 关键词：     

叠氮化钡的高压拉曼光谱研究

在室温条件下,利用金刚石对顶砧高压技术,对叠氮化钡进行了原位高压拉曼光谱研究,采用红宝石荧光压标测压,实验的最高压力为10 GPa。实验压力范围内拉曼光谱随压力增加发生了丰富的变化。由于多处拉曼峰的出现和消失并伴随频移有拐点,我们判断叠氮化钡在3 GPa左右时发生了第一次结构相变;随着压力继续增加,在3.5~6.5 GPa范围内拉曼光谱仍不断变化,我们判断可能是相变或者是N=N=N键角和两个键长的非对称压缩导致的;压力继续增加,在8 GPa左右,多处新峰出现和峰的劈裂表明又发生了一次结构相变,并且判断叠氮化钡向着更复杂的结构转变。通过实验可以确定,实验压力范围内N=N=N离子并未被破坏。其实验结果有待高压同步辐射实验的进一步确认。     

钛酸锶钡材料在外加电场作用下的拉曼光谱研究

采用传统的固相反应烧结方法制 备Ba_xSr_1-xTiO₃（0.40≤ x ≤0.70）陶瓷,借助于Raman散射光谱,研究了陶瓷样品在不同原位电场作用下Raman振动模式的变化,观察到居里温度附近显著的电场诱导的四方–立方相之间的转变. 结果表明A₁（TO₃）和E（TO₄）两种振动模式与晶体的结构存在密切的联系,这两种模式源于O-Ti-O沿晶格中c轴的方向和ab面内的振动. A₁（TO₃）/E（TO₄）之间Raman峰的相对强度比,随外加场强的增加明显升高,顺电相逐渐转变为铁电相,晶格的畸变越来越明显,其宏观性能上表现为介电常数的降低,可调率的增加. 同时对居里温度附近电场诱导的结构相变对顺电相下介电非线性的贡献进行了探讨. 关键词： 钛酸锶钡 Raman散射光谱 结构相变     

钛钡硼硅酸盐玻璃结构激光拉曼光谱研究

用激光拉曼光谱系统研究了含钛钡硼硅酸盐玻璃的结构。结果表明ＴｉＯ２含量较低时Ｔｉ４＋主要处于［ＴｉＯ４］中。当ＴｉＯ２摩尔含量约为２０％时，有少量［ＴｉＯ６］形成。当玻璃中Ｔｉ４＋和Ｂ３＋共存时，Ｂ２Ｏ３含量的变化不会改变Ｔｉ４＋的结构状态。但ＴｉＯ２的存在将促进部分Ｂ３＋由［ＢＯ４］转化成［ＢＯ３］，并将这一现象称为“钛硼结构效应”     

钡原子6p3/2ns自电离里德伯态的研究

用激光多步激发技术研究了处于６ｐ１／２电离限以下的６ｐ３／２ｎｓ自电离态的光谱。并利用最 Ｒ矩阵的计算结果,结合多通道量子亏损理论进行了理论分析,理论结果与实验光谱相符合。     

用含时密度泛函理论计算钠原子跃迁光谱

运用含时密度泛函理论和局域密度近似方法，计算出了Na原子的多个激发态能级和各能级电子波函数的实空间分布，并从中分析出其跃迁光谱Rydberg序列的主要特征谱线. 计算结果与实验数据符合得较好，充分验证了密度泛函激发态理论的有效性. 关键词： TDDFT 激发态 跃迁光谱 Na原子     

元素钡对X射线荧光光谱法测定铁矿中全铁的修正作用

用X射线荧光光谱法分析铁矿石的全铁,在绘制校准曲线时加入钡的修正,可改善曲线质量,提高分析准确度.     

二聚物在Cu表面上的扩散和解离研究

利用分子动力学模拟统计了几种不同温度下三种不同二聚物(Cu₂, Ag₂和Pd₂)在铜衬底(100), (111)表面上的扩散和解离行为, 探讨同质和异质二聚物在Cu表面上扩散和解离的特点; 采用分子动力学中的静态计算方法计算了这三种二聚物在扩散和解离过程中的能量势垒, 并与动力学模拟、二聚物与衬底的结合能等结果进行了比较, 探讨二聚物扩散和解离过程与扩散势垒、结合能、表面性质和温度等的关系. 原子间相互作用采用半经验EAM势. 结果表明: 同质和异质二聚物在各个不同表面上的扩散势垒、解离势垒有一定的规律, 并和二聚物与衬底的结合性质有关; 二聚物是否易解离与衬底表面的结构以及二聚物与衬底的结合性质关系密切; 二聚物解离前协同扩散的快慢与二聚物和衬底的结合性质以及二聚物在表面的扩散和解离势垒密切相关.     

Crystal-chemical aspects of phase transitions in barium titanate

Structural aspects of phase transitions in barium titanate are analysed from a crystal-chemical point of view. The respective discussion is focused on two possible sources of ferroelectric deformation of TiO₆⁸⁻ octahedron. First, gradual changes of π-electron localisation are considered. Under an assumption of a mean field related to actual crystal symmetry, an adequate model is proposed. The values of bond orders are evaluated from resonance structures. They are compared with respective bond lengths. Another source of the ferroelectric deformation, which is taken into consideration, relates to the Ti-ion movements between eight potential minima on the cube diagonals. The analysis of the problem is grounded within adiabatic (local field) approximation and follows ideas of an eight-site model. The crystal structure is treated as a result of averaging of atomic positions according to the postulated disorder. Comparison of the X-ray interatomic distances with the values calculated from the disorder model is made. The collected data generally prove that the ferroelectric deformation of the TiO₆⁸⁻ octahedron, which is observed in barium titanate, contains two components. One is related to the changes of structural disorder degree and should be considered as a main factor. The other includes the effects attributed to the changes of π-electron localisation.     

Anomalous atmospheric absorption spectra due to water dimer

The anomalous atmospheric absorption spectra in the window wavelength region of 8–14 um have been suggested due to the water dimer. Based on our laboratory measurements, water continuum CO₂ laser absorption spectra and a resonance absorption line due to the weak local water vapor pure rotational transition have been reported. The equilibrium concentration of water dimers in the atmosphere, the electronic binding energy and the theoretical calculations for absorption attenuation have been obtained in agreement with published data.     

The infrared spectrum of the CO dimer

The infrared spectrum of (¹²C¹⁸O)₂ has been studied for the first time using a tunable diode laser spectrometer in the 2095 cm⁻¹ region to probe a pulsed supersonic jet expansion. Very dilute gas mixtures of CO in He were used, resulting in small consumption of ¹²C¹⁸O sample gas, as well as cold and simple spectra. The results were analyzed using a term value scheme to obtain model-independent energies for 7 rotational levels belonging to 2 stacks in the lower state, v_CO=0, and 22 levels belonging to 7 stacks in the upper state, v_CO=1. The two ground state isomers of the CO dimer were found to be separated by only 0.639 cm⁻¹ for (¹²C¹⁸O)₂. These results provide a foundation for future studies of the millimeter wave spectrum.     

Specific heat of super carbon nanotube and its chirality independence

The specific heat of the super carbon nanotube (ST) was investigated by the molecular structure mechanics method. At given temperature, it was found that the specific heat of the ST is a fixed value and is almost independent both of the length, diameter and of chirality of the ST. By comparing the influences of the chirality of the ST on its mechanical properties, electronic properties and thermal properties as well, we find that the chirality effects on the physical properties of STs can be neglected. This result may be regarded as a universal law for the physical properties of STs.     

Entanglement and decoherence in a quantum dimer

The dynamical properties of quantum entanglement in an integrable quantum dimer are studied in terms of the reduced-density linear entropy with various coupling parameters and total boson numbers. The characteristic time of decoherence process in the early-time evolution of the linear entropy is obtained, indicating that the characteristic time and the corresponding entropy exhibit a maximum near the position of the corresponding classical separatrix energy.     

水二聚体分子间相互作用势

利用超分子二阶到四阶多体微扰理论和扩展的相关一致基组(aug-cc-pVTZ)结合有效的中点键函数(3s3p2d1f1g)计算水二聚物的平衡结构和分子间相互作用势,并用平衡方法修正基组重叠误差.在MP2/aug-cc-pVTZ理论级别优化水二聚物几何构型.与正常优化的结果相比,平衡修正优化得到的RO-O和α值分别轻微的增加0.002 nm和0.19°,同时,θ值减小0.013°.在MP2水平利用扩展的相关一致基组结合有效键函数,预言了RO-O和ΔECP值分别为0.0923 nm和-4.86 kcal/mol,计算结果与实验值符合得很好.用exp-4.2势函数拟合分子间相互作用能的离散点,拟合结果与从头算计算的结果一致.     

Tunable Fano resonances and plasmonic hybridization of gold triangle–rod dimer nanostructure

A gold dimer structure consisting of a notched triangle nanoslice and a rectangle nanorod is proposed to produce distinct Fano resonance. Owing to the coupling between the dipole plasmon mode of the nanorod and the dipole or quadrupole plasmon mode of the nanoslice, the extinction spectrum with a deep Fano dip is formed and can be well fitted by the Fano interference model for different geometry parameters. In addition, Fano resonance of the gold dimer nanostructure also intensely depends on the polarization direction of incident light. Moreover, Fano resonance of the triangle–rod trimer is also analyzed by adding another nanorod into the former dimer and exhibits the splitting of plasmonic resonant peak in high order coupling modes. The plasmonic hybridizations in these nanostructures have been analyzed for revealing the physical origin of the Fano resonance.     

共上能级三能级二聚物蒸气系统增益系数测量

本文提出了一种能够测量单纯由粒子数反转造成的增益系数的方法,给出了考虑几何因素及吸收影响之后修正了的实验计算公式,并对Na_2B~1Ⅱ_u—X~1∑_g~+跃迁增益系数进行了测量。     

Bound-free transitions and the dissociation limit

Following a sequential two-photon excitation, fluorescence is observed from several selectively excited single rotational-vibrational energy levels of theE ³ π0 _g ⁺ state of molecular iodine. The re-emittedE →B fluorescence spectrum from each of the populated rovibrational level of theE state consists of a series of sharp lines terminating on the various discrete ro-vibrational levels of theB state and a few broad lines due to transitions taking place on to the continuum of theB state. The point of transition from sharp lines to broad features in the fluorescence spectrum has been utilized to determine theB state dissociation limit. This method of obtaining the dissociation limit of the molecular electronic states appears to be quite simple and straightforward.