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.     

探测二茂铁外价轨道(e,2e)反应中的扭曲波效应

利用第三代高效率电子动量谱仪,分别在600和1500 eV两种不同入射电子能量下获得了二茂铁(ferrocene)分子外价轨道的电离能谱和电子动量谱的相关实验结果.并利用非相对论与标量相对论密度泛函方法计算出了二茂铁的重叠型和交错型两种不同构象的理论动量谱.两种构象的外价轨道一一对应,理论电子动量谱基本一样.对二茂铁的外价轨道,在低动量区观测到了强烈的扭曲波效应,这与这些轨道主要由铁原子的3d轨道构成有关.通过相对论和非相对论计算结果的比较,表明相对论效应对于二茂铁的外轨道动量分布几乎没有影响. 关键词： 二茂铁分子 电子动量谱 相对论效应 扭曲波效应     

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.     

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.     

异二氯乙烯价壳层轨道电子结构的电子动量谱研究

本文报道了异二氯乙烯分子价壳层轨道电子结构的电子动量谱研究.实验由一台(e,2e)电子动量谱仪在非共面对称的几何条件下开展,入射电子能量为1200 eV.实验获得了异二氯乙烯价壳层各个轨道的电离能谱和电子动量分布.采用Hartree-Fock方法和密度泛函方法结果与实验数据基本一致.研究发现,干涉效应会对2a_2和5b_2这两个Cl孤对电子轨道的电子动量分布产生显著影响.     

异二氯乙烯价壳层轨道电子结构的电子动量谱研究（英文）

本文报道了异二氯乙烯分子价壳层轨道电子结构的电子动量谱研究.实验由一台(e,2e)电子动量谱仪在非共面对称的几何条件下开展,入射电子能量为1200 eV.实验获得了异二氯乙烯价壳层各个轨道的电离能谱和电子动量分布.采用Hartree-Fock方法和密度泛函方法结果与实验数据基本一致.研究发现,干涉效应会对2a_2和5b_2这两个Cl孤对电子轨道的电子动量分布产生显著影响.     

Electron Momentum Distributions for 4a1 Orbitals of CFxCl4-x in Low Momentum Region: a Possible Evidence of Molecular Geometry Distortion

由于低动量区域理论和实验的严重差异,重新分析了系列氟利昂分子CF₃Cl、CF₂Cl₂和CFCl₃ (CF_xCl_4-x, x=1～3)的4a₁轨道的电子动量分布. 利用分子离子的平衡几何构型计算得到的动量分布很大地改善了,与实验数据之间的吻合,这一结果表明在p<0.5 a.u.区域实验观测到的偏高的动量分布值可能是电离瞬间分子构型的扭曲带来的. 进一步的分     

碘甲烷分子内层轨道的电子动量谱学研究（英文）

本文利用电子动量谱仪在1200 eV电子碰撞能量下测量了碘甲烷分子内层轨道电子束缚能谱和电子动量分布.在能谱上观测到自旋-轨道耦合作用导致的两个分裂峰,得到了它们对应的电子动量分布.采用相对论密度泛函理论方法计算了自旋-轨道分裂成分的电子动量分布,计算结果在电子动量大于1.0 a.u.区域内与实验测量符合很好,但在动量小于1.0 a.u.区域内严重低估了实验.扭曲波理论计算很好地解释了低动量区的实验结果.     

碘甲烷分子内层轨道的电子动量谱学研究

本文利用电子动量谱仪在1200 eV电子碰撞能量下测量了碘甲烷分子内层轨道电子束缚能谱和电子动量分布. 在能谱上观测到自旋-轨道耦合作用导致的两个分裂峰,得到了它们对应的电子动量分布. 采用相对论密度泛函理论方法计算了自旋-轨道分裂成分的电子动量分布,计算结果在电子动量大于1.0 a.u.区域内与实验测量符合很好,但在动量小于1.0 a.u.区域内严重低估了实验. 扭曲波理论计算很好地解释了低动量区的实验结果.     

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…     

Dissociative electron attachment to CF2Cl2

Using a recently constructed high resolution crossed electron/molecular beam apparatus consisting of a hemispherical electron monochromator and a quadrupole mass spectrometer we have measured the relative production cross sections for CI^– and F^– via electron attachment to CF₂Cl₂. The relative Cl^– cross section is placed on an absolute scale by reference to an absolute rate coefficient using a calibration method involving integration of the measured anion signal. The most efficient Cl^– production process is at about zero energy and its magnitude is resolution limited. The present high resolution value of 6 × 10^–16 cm² compares well with an earlier value reported by Chen and Chantry. A second peak is detected at around 0.8 eV in accordance with some of the earlier beam and swarm measurements. The observed production of F^– has an appearance energy of 1.9 eV and the energy of maximum cross section is 3.36 eV, the latter value comparing well with several previous studies.     

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.     

Infrared multiphoton dissociation of13CF3Cl induced by CO2 laser pulses

Selective infrared multiphoton dissociation of¹³CF₃Cl induced by CO₂ laser pulses adjusted on = 1071.9 cm^–1 has been studied in the energy rangeE between 0.5 and 2 J per laser pulse or fluence range between 5 and 25 J per cm², and in the pressure range between 0.10 and 60 Torr. The effect of these parameters on the isotopic selectivity of the dissociation gives information on the rotational relaxation constants. As for the dissociation probabilities, they vary exponentially withE ^–1. The applicability of such an Arrhenius-type relation is discussed and semi-quantitatively justified.     

High-resolution spectroscopy of CF2Cl2 in a molecular jet

Absorption spectra of CF₂Cl₂ were recorded around 923 cm^–1, with a resolution of 50 MHz. The application of the molecular jet technique considerably simplifies the spectra as compared to room-temperature experiments. Rotational and vibrational temperatures were measured for CF₂Cl₂ pure and seeded in Ar or He. Molecular constants were obtained for thev ₆ vibrational band of the two most abundant chlorine isotopic species, as well as vibrational band origines for thev ₆±v ₄ and thev ₆±v ₅ hot-bands of the CF₂ ³⁵Cl₂ isotope.Guest     

A Modified Potential Method for Electrons Scattering Total Cross Section Calculations on Several Molecules at 30 ～ 5000 eV: CF4, CCl4, CFCl3, CF2Cl2, and CF3Cl

A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is employed to calculate the total cross sections (TCSs) for electrons scattering from several molecules (CF4, CCl4, CFCl3, CF2 Cl2, and CF3 Cl) over an incident energy range 30 ～ 5000 eV using the additivity rule model at Hartree-Fock level. The quantitative TCSs are compared with those obtained by experiments and other theories wherever available, and good agreement is obtained above 100 eV.It is shown that the modified potential can successfully calculate the TCSs of electron-molecule scattering over a wide energy range, especially at lower energies.     

Effect of rotational relaxation on the yield of the multiphoton dissociation of CF3Cl and CF3Br under TEA-CO2 laser pulses

The yield of the multiphoton dissociation of CF₃Cl and CF₃Br induced by TEA-CO₂ laser pulses has been studied in the pressure range between 0.25 and 8 Torr, the laser wavelength being chosen so as to excite preferentially the minor isotopic components¹³CF₃Cl and¹³CF₃Br. For both compounds the dissociation probability is found either to increase almost linearly or to decrease monotonously with gas pressure, according as the laser beam is focused or unfocused, respectively. This behaviour is explained by rotational relaxation effects, and a value of 22ns·Torr for the rotational self-relaxation time of CF₃Cl is obtained.     

Laser-Induced Current Switching Observed in the Discharge Media of CF2Cl2-N2 and CH3Cl-N2

Switchings of discharge current induced by ArF and KrF laser pulses in the discharge media of CF2Cl2-N2 and CH3Cl-N2 were investigated using a negative point-to-plane discharge apparatus. The electron attachment rate constants of CF2Cl2 in buffer gases of N2 and Ar were measured by a parallel-plate drift-tube apparatus at various E/N, from which the dominant negative ions in the discharge media were inferred. The conductivity of the discharge medium is enhanced upon laser irradiation due to conduction electrons being produced from photoelectron-detachment of Cl-. From the dependence of the enhanced current on laser power, the photodetachment cross sections of Cl- in a given discharge condition were derived to be 2.5 × 10-17 cm2 at 193 nm and 1.0 × 10-17 cm2 at 248 nm. After the current enhancement, the current was greatly reduced as was observed in the discharge medium of CF2Cl2-N2, but not in CH3Cl-N2. The mechanism for the optically induced reduction of discharge current is discussed.