SF6电子动量谱学研究中干涉效应的观测

利用非共面对称的高效率(e,2e)电子动量谱仪测量了SF₆分子外价分子轨道的二维电子能量- 动量密度谱. 通过理论计算与实验结果的比较,发现B3LYP密度泛函理论计算结果可以较好地解释实验测量的轨道电子动量分布. 此外,对于最外层的4个来自F2p孤对电子贡献的非键分子轨道,实验上观测到非常明显的多中心干涉图样.     

用(e,2e)电子碰撞电离测量乙烯分子中的扭曲波效应

利用新一代高性能（e,2e）电子动量谱仪,在400-2400 eV的大范围入射电子能量条件下,测量了乙烯分子电子密度的动量分布.实验测量的乙烯1b3g轨道电子动量分布与平面波冲量近似的理论计算结果相比,在低动量区和高动量区出现明显的上翘（turn up）效应,并且此上翘效应随着入射电子能量的增加而逐渐减小.进一步的分析证实由于分子的扭曲波效应引起1b3g轨道动量分布在低动量区和高动量区的上翘.实验测量结果将对分子扭曲波理论计算的建立提供实验依据.     

二氧化碳分子3σu轨道的电子动量谱测量

自从70年代实现（e,2e）电子动量谱测量以来,电子动量谱学获得了巨大的发展,成为探测物质结构的强有力的手段[1]。它可以分辨壳层来获得原子分子价壳层轨道的动量空间的电子密度分布,尤其是对低动量端的电子分布非常敏感。二氧化碳分子是一种典型的线性分子,对其结构的深入研究,具有相当的应用价值,尤其在环境保护领域。以前,CO2分子的电子动量谱曾被测量过三次[2-4],但由于能量分辨或动量分辨较低,研究结果不能令人满意。因此,用电子动量谱学的实验手段,进一步研究CO2分子,是非常有意义的。……     

CFCl3分子2e和4a1轨道的电子动量谱研究

由于工业的迅速发展 ,使得空气质量急剧下降 ,因此对影响大气的分子进行深入研究变得非常必要 .本实验室已经对影响环境的甲烷[1] 、丙烷[2 ] 、CO2 [3] 等分子进行了电子动量谱研究 ,为环保提供了有用的数据 .CFCl3作为工业广泛应用的气雾剂和制冷剂原料 ,它的大量使用导致了大气中臭氧的减少[4 ] .前人已用光电子谱学的方法[5- 8] 研究了CFCl3,我们又用电子动量谱的手段对CFCl3分子进行了进一步的研究 ,即从波函数的层次上详细了解CFCl3的电子结构 .(e ,2e)电子动量谱学在研究分子的电子结构方面有非常独特的优越性[9- 12 ] ,它可以…     

生物有机分子构像分析的新探针研究

通过轨道电子密度分布研究生物有机分子构像,可获得区别于现有研究手段所能得到的结果.对基于(e,2e)散射实验的电子动量谱学作为一种生物有机分子构像分析的方法进行了探讨.     

乙醇分子的高分辨电子动量谱学研究:单个构象异构体的轨道电子动量分布

利用高分辨电子动量谱仪测量了乙醇分子外价轨道的电离能谱,通过对一系列角度关联的电离能谱进行解谱,获得了各个电离能峰对应的分子轨道电子动量分布.利用密度泛函理论方法计算了乙醇分子两种构象异构体的轨道电子动量分布,通过与实验结果进行比较,发现实验测量的电离能为14.5和15.2 eV能峰对应的电子动量分布分别与理论计算的单个构象异构体trans 8a''和gauche 9a轨道电子动量分布符合较好.     

Electron Momentum Spectroscopy of Ethanethiol Complete Valence Shell

利用(e,2e)电子动量谱学手段首次测量了乙硫醇分子全部价轨道的束缚能谱和电子动量分布. 谱仪采用非共面对称的运动学条件,入射电子能量为1.2 keV加束缚能. 实验结果与密度泛函和Hartree-Fock方法的理论计算结果基本相符. 在束缚能谱中,观察到了17.8 eV的可能的伴线,并用电子动量谱进行了研究和标识.     

环己烯分子2b和3a轨道的电子动量谱学研究

报道了环己烯(C6H10)分子2b和3a轨道电子动量谱的首次研究,并且给出了价轨道的电离能谱信息,实验在非共面对称几何条件下的能量多道型电子动量谱仪下完成,入射电子的能量为1200eV加结合能.通过Hartree-Fock和密度泛函方法计算得到了C6H10分子2b和3a轨道的动量谱,在动量大于0.25a.u.区域理论与实验结果符合较好,实验结果与理论计算相比在低动量端出现“上翘”的现象,这可能是由于分子的扭曲波效应引起的.     

2-氟乙醇分子外价轨道的电子动量谱学

利用不共面不对称(e,2e)谱仪测量了2-氟乙醇分子外价分子轨道的束缚能谱和电子动量分布,并用外价格林函数方法和密度泛函理论计算了分子的电离能和轨道波函数. 通过理论计算与实验结果的比较,明确标识了实验测量的电离能谱. 考虑了2-氟乙醇分子五种异构体的玻尔兹曼热力学统计权重后,理论计算的电子动量分布能够较好地解释实验测量结果.     

环戊烷分子的1e1″轨道电子密度

从实验和理论上研究了环戊烷分子的 1e″1轨道电子动量谱分布 .理论计算采用Hartree Fock方法和密度泛函理论 ,给出了该轨道的位置空间的密度分布图 .对环戊烷分子的电子动量谱研究在国内首次将分子样品的研究由气态扩展到了液态. The spherically averaged momentum distributions for cyclopetane have been investigated by experimental measurements and theoretical calculations. Theimpact energy is 1 200 eV plus binding energy and a symmetric non-coplanar kinematics is employed. The theoretical calculations are obtained by using Hartree-Fock method and Density Function Theory. The position density for 1e ″ 1 orbital is reported.     

13C-selective IRMPD of CBr2F2/Cl2 and CCl2F2/Br2 systems

The CO₂ TEA laser irradiation of CBr₂F₂ in the presence of Cl₂ yielded ¹³C-enriched CBrClF₂ and ¹³C-enriched CCl₂F₂ under selected experimental conditions. As the photolysis proceeded, the ¹³C concentration of CBrClF₂ decreased gradually and that of CCl₂F₂ increased up to 90% or higher. These results can be explained by the mechanism involving the secondary ¹³C-selective IRMPD of the primary product CBrClF₂. On the other hand, the carbon-containing product for a CCl₂F₂/Br₂ system was only CBrClF₂; the further IRMPD of which probably regenerated CBrClF₂ in the presence of Br₂. The decomposition probabilities of ¹²C- and ¹³C-containing molecules in both systems were measured as functions of laser line, laser fluence, and reactant pressures.     

μ+SR study of LaNi2As2, URh2Si2 and CeRh2Si2

Muon spin relaxation experiments have been carried out in the paramagnetic and magnetically ordered states of URh₂Si₂ and CeRh₂Si₂. As the magnetic structure of these compounds is well known, these measurements can help to characterise their magnetic properties probed by μSR and to understand the μSR results of the heavy fermion compounds of the same crystallographic family. Our measurements show that the muons occupy two different crystallographic sites. The spectra of URh₂Si₂ and CeRh₂Si₂ in the magnetically ordered states are very different, probably reflecting their different magnetic structures. The spectra obtained on CeRh₂Si₂ are similar to the published spectra of the heavy fermion compound CeCu_2.1 Si₂. Muon spin rotation measurements on LaNi₂As₂ indicate that the muon is diffusing at 150 K.     

Magnetostriction of SmMn2Ge2 and GdMn2Ge2 intermetallic compounds

Longitudinal and transverse magnetostrictions of polycrystalline samples of intermetallic compounds RMn₂Ge₂ (R=Sm or Gd) are measured in pulsed magnetic fields up to 250 kOe. It is found that linear magnetostrictive strains of about 10^?3 arise in a temperature range in which the magnetic field causes a change in the magnetic state of a manganese magnetic subsystem. The results obtained are described within the model of a two-sublattice ferrimagnet with a negative exchange interaction in the manganese subsystem in terms of a strong dependence of this interaction on interatomic distances.     

Eu2+掺杂CaSi2O2N2荧光粉发光性能

采用固相反应法合成了组成为Ca_1-xEu_xSi₂O₂N₂的Eu²⁺掺杂CaSi₂O₂N₂荧光粉.通过荧光光谱对样品的发光性能进行了研究,发现Eu²⁺掺杂CaSi₂O₂N₂荧光粉发射光谱为宽波段的单峰结构,主要包含绿光和黄光区,发射峰在556~568 nm.从发射光谱的宽带特征来看,CaSi₂O₂N₂:Eu²⁺的发射主要对应着Eu²⁺离子4f⁶5d→4f⁷跃迁.从激发光谱所覆盖的范围还可以看到,样品可以有效的被UV蓝-光激发,这意味着该类荧光粉在白光LED方面有可能得到广泛的应用.另外,样品的发光性能与激发离子的浓度有着很大关系.激发离子浓度增大时,发射光谱会发生明显红移.利用这一性质,可以通过改变Eu²⁺浓度来调节荧光粉的发光范围,从而满足不同场合的需要.同时,Eu²⁺浓度提高,样品发射光谱的强度也会随之增强,在x=0.06时发射强度达到最大值,之后继续增加Eu²⁺浓度,强度不仅没有增加反而降低,即出现浓度猝灭现象.     

CO2-laser-induced multiphoton absorption of CF2Cl2

Energy absorption by CF₂Cl₂ from an intense TEA CO₂ laser pulse is measured as a function of the pressure of CF₂Cl₂ and the pressure of Ar bath gas for different laser energy fluences. The fraction of the molecules excited by the laser field and the average energy of the molecular ensemble are determined by a simple experimental method.     

X-ray photoemission spectra measurements of CeNi2Sb2 and CeCu2Sb2

X-ray photoemission spectra, resistivity and susceptibility of CeNi₂Sb₂ and CeCu₂Sb₂ were measured and are discussed. The results indicate that these alloys are Kondo systems. For comparison of the valence band properties, the spectra of the isostructural alloys of RT₂X₂-type with R = La, Gd, T = Cu, Ni and X = Sn, Sb were investigated, too.     

Synthesis and properties of HgI2 intercalation of Bi2Sr2CaCu2Oy superconductor

Polycrystalline or single crystals of HgI₂ intercalated Bi₂Sr₂CaCu₂O_y (Bi2212) have been synthesized and their properties have been studied together with those of HgBr₂ intercalates. Single crystals of HgI₂ intercalated Bi2212 were synthesized by a stepwise intercalation method using iodine intercalate as a secondary host material. These could not be obtained through direct intercalation methods by which polycrystalline sample were obtained. From ac susceptibility and resistivity measurements, superconducting onset temperature (T_con) for polycrystalline HgI₂ intercalate was found to be 82 K which was higher than that of the host (75 K). On the other hand, T_con for single crystal HgI₂ intercalate was shown to be 79–80 K which is lower than that of host (95–97 K). The effect of HgI₂ or HgBr₂ intercalation on T_c tried discussion from the view point of hole doping and interblock coupling effect.     

Infrared observation of OC-C2H2, OC-(C2H2)2 and their isotopologues

ABSTRACT

The fundamental band for the OC-C₂H₂ dimer and two combination bands involving the intermolecular bending modes ν₉ and ν₈ in the carbon monoxide CO stretch region are re-examined. Spectra are obtained using a pulsed supersonic slit jet expansion probed with a mode-hop free tuneable infrared quantum cascade laser. Analogous bands for OC-C₂D₂ and the fundamental for OC–DCCH as an impurity are also observed and analysed. A much weaker band in the same spectral region is assigned to a new mixed trimer, CO-(C₂H₂)₂. The trimer band is composed uniquely of a-type transitions, establishing that the CO monomer is nearly aligned with the a-inertial axis. The observed rotational constants agree well with ab initio calculations and a small inertial defect value indicates that the trimer is planar. The structure is a compromise between the T-shaped structure of free acetylene dimer and the linear geometry of free OC-C₂H_2. A similar band for the fully deuterated isotopologue CO-(C₂D₂)₂ confirms our assignment.