Electronic spectra of aliphatic carbonyl compounds by electron impact spectroscopy: II. Saturated ketones

Electron impact energy loss spectra of acetone, 2-butanone, methyl isobutyl ketone, methyl isopropyl ketone, and methyl tertiarybutyl ketone have been recorded at an impact energy of 100 eV and a scattering angle of two degrees. Rydberg assignments have been made using quantum defects and term values obtained by reference to ionization potentials measured by photoelectron spectroscopy. Substituent effects on Rydberg orbital energies are discussed using Taft σ* values.     

Angular distribution of EELS intensities: CO on Pt(111)

We present the angular distribution of inelastic intensities corresponding to the excitation of the vibrational modes of CO chemisorbed on Pt(111). The experimental values are compared with those predicted by dipole scattering. All the vibrational modes, including the C-metal, stretch, show experimental values larger than theoretical ones. The difference is attributed to vibrational excitation by impact scattering. The impact scattering cross section is found to be energy dependent and increases for low primary energies (2 eV). The differential cross section is, however, smaller than that observed for resonant scattering in free CO.     

Debye等离子体中高能H++H碰撞激发过程的研究

利用碰撞参数玻恩近似方法研究了Debye 等离子体环境中高能H⁺+H的碰撞激发过程, 研究了不同Debye 半径下氢原子1s → 2p 的激发耦合相互作用矩阵元、入射粒子能量为160 keV/u 的激发电子跃迁概率以及入射粒子能量范围为100–1000 keV/u 的碰撞激发截面. 结果表明: 随着屏蔽效应的增强, 激发截面减小. 根据激发截面的公式以及计算结果详细分析了引起激发截面减少的原因. 入射粒子与激发电子之间的屏蔽相互作用势和靶的电子结构(波函数和能级) 对激发截面都有很重要的影响. 关键词： 等离子体 碰撞参数玻恩近似方法 碰撞激发截面     

Rotational excitation of H2O by cold electrons

Experimental data are presented for the scattering of electrons by H2O between 17 and 250 meV impact energy. These results are used in conjunction with a generally applicable method, based on a quantum defect theory approach to electron-polar molecule collisions, to derive the first set of data for state-to-state rotationally inelastic scattering cross sections based on experimental values.     

20MeV到180MeV／u~（16）O＋~（197）Au系统的BUU计算：线动量与角动量转移依赖碰撞参数与能量研究

用考虑了角动量守恒的ＢＵＵ模型计算了２０ＭｅＶ≤Ｅ／ｕ≤１８０ＭｅＶ能区１６Ｏ＋１９７Ａｕ系统的反应线性动量转移（ＬＭＴ）及余核角动量，着重讨论了反应线性动量转移及余核角动量对反应碰撞参量、入射能Ｅ／ｕ的依赖关系，比较了计算ＬＭＴ与Ｖｉｏｌａ系统性给出的结果间的偏差．计算结果揭示了当Ｅ／ｕ≥９０ＭｅＶ时，余核角动量对Ｅ／ｕ增长出现的饱和现象，主要来源于靶核对弹核捕获能力的持续丢失．     

Entstehung von Alkalimetallen bei der Elektronenbestrahlung von Alkalihalogeniden

We have observed additional peaks in the energy loss spectra of NaBr, NaI, KF, KI, and RbF foils, which are caused by the electron impact. They are identified as volume and surface plasma losses of alkali metal particles. The energy loss values are in accord with energy loss data of alkali metal foils. Electron diffraction patterns of the irradiated alkali halide foils showed additional rings of alkali metal agglomerates, the size of which are estimated to be in the range of 100Å.     

Rydberg states of HCN observed by electron impact spectroscopy

The electron energy loss spectrum of HCN has been determined in the energy region 8–13.6 eV at impact energies of 100, 50 and 30 eV. It is shown that energy loss spectra of HCN at intermediate impact energies can be satisfactorily analysed unlike the diffuse unassigned optical absorption spectra that have previously been reported. Rydberg series have been assigned using term values and quantum defects together with ionization potentials obtained by photoelectron spectroscopy.     

Computer simulation of back sputtering and ion penetration into polycrystalline targets

Pramana - In the present work computer simultations of the back sputtering of low energy neon ions with low impact parameter and the penetration of the same for higher values of the impact...     

Application of the Modified BUU Model to Reaction Induced by 16O on 197An at 20MeV≤E/u≤180 MeV:Dependence of the Angalar and Linear Momentum Transfer on Impact Parameter and Energy

The angular and linar momentum transfered to target residue on 20 to 180MeV/u ¹⁶O+¹⁹⁷Au system are calculated with BUU(Boltzmann-Uehling-Uhlenbeck) model in which the angular momentum conservation is added.The dependence of angular and linar momentum on impact parameter and incident energy is discussed.The deviations between calculated values of(1mt) and those from viola system are compared.The results of the simulations suggest that the saturation of angular momentum transfer with incident energy increase mainly comes from the loss of capture ability of the target on projectile.     

Electronic spectra of aliphatic carbonyl compounds by electron impact spectroscopy: III. Unsaturated compounds

Electron impact energy loss spectra at an impact energy of 100 eV and a scattering angle of 2 degrees are presented for propenal (CH₂ = CHCHO) and methyl vinyl ketone (CH₂ = CHCOCH₃). The spectra are tentatively assigned using quantum defects and term values derived from ionization potentials measured by photoelectron spectroscopy. The duality of Rydberg and valence transition assignments in propenal is discussed. It is shown that a transition earlier assigned by Walsh to be π → π* is most probably a Rydberg transition.     

Energy transfer under impact load studied by molecular dynamics simulation

The process of amorphous silica clusters impact on a crystal silicon substrate is studied by molecular dynamics simulation, focusing on the energy transfer between clusters and the substrate under different impact conditions such as cluster size, impact velocity, and incidence angle. The impact process is divided into cluster deformation stage, cluster resilience stage, and cluster rebound stage according to the courses of energy change during the impact process. The simulation elucidates that the time of impact process of every cluster is only related to cluster size and is independent of impact velocity and incidence angle. The translational energy loss of the cluster and the potential energy increment of the substrate during cluster deformation stage, and the dissipation energy of system are independent of cluster size under the same impact energy and incidence angle. And the translational energy loss of the cluster during cluster rebound stage changes from energy absorption to energy release after the incidence angle becomes more than 60°. The rotational energy of the cluster may be omitted when the incidence angle is less than 15°. The ratios of the rotational energy increment of the cluster, the kinetic energy increment, and the potential energy increment of the substrate to the translational energy loss of the cluster are obviously influenced by impact conditions. And the ratios of the increment of the other categories of energy to the translational energy loss of the cluster are not sensitive to impact conditions.     

Ionization of K-shell electrons by electron impact

We have investigated the universal scaling behavior for cross sections of the single K-shell ionization by electron impact. The calculations are performed within the framework of non-relativistic perturbation theory, taking into account the one-photon exchange diagrams. Special emphasis is laid on the near-threshold energy domain. The results obtained are applicable for wide family of atomic targets with moderate values of the nuclear charge Z.     

基于离散元方法的颗粒材料缓冲性能及影响因素分析

在冲击荷载作用下, 颗粒材料通过颗粒间的摩擦及非弹性碰撞可有效进行能量耗散实现缓冲作用. 本文采用离散元方法对冲击载荷下颗粒材料的缓冲过程进行数值分析, 研究不同厚度下颗粒材料的缓冲性能. 计算结果表明: 颗粒层厚度H是影响颗粒材料缓冲性能的关键因素, 并存在一个临界厚度H_c. 当H < H_c时, 冲击力随H的增加而降低; 当H > H_c时, 冲击力对H的变化不敏感并趋于稳定值. 此外, 在不同颗粒摩擦系数和初始密集度下对缓冲过程的离散元分析表明, 光滑和疏松颗粒材料具有更好的缓冲性能. 最后, 对颗粒材料在冲击过程中的力链结构和底板的压力分布进行了讨论, 以揭示颗粒材料缓冲性能的内在机理.     

Simulation of sputtering and desorption of gold nanoclusters under bombardment with 180-eV/atom Au400 nanoclusters using the classical molecular dynamics method

Computer simulation of the interaction of an Au₄₀₀ nanocluster (the total energy E = 72 keV) with free spherical Au _N nanoclusters (6 and 12 nm in diameter) and Au₆₀₅₁ clusters deposited on the (111) surface of an Al substrate is performed by means of the classical molecular dynamics method. The distributions of the absorbed energy (ε) converted to one atom of the bombarded nanocluster and the sputtering yield are analyzed. It has been ascertained that the most probable values are either the small (ε ? ε_max = E/N) or the maximum possible (ε ～ ε_max) values of absorbed energy. The total sputtering yield and the absorbed energy decrease with increasing impact parameter. It has been demonstrated that, with a probability of ～10%, a direct impact can lead to ejection of the entire bombarded nanocluster from the substrate. This event occurs in the case where an incident cluster initiates the secondary emission of target-cluster atoms mainly in the direction of the substrate. As a result, the nonsputtered part of the target cluster acquires the momentum in the opposite direction. This recoil effect can be regarded as one of the possible mechanisms by which nanoclusters deposited on substrate surfaces desorb under ion and cluster bombardment.     

Nanofriction studies of reactively or non-reactively cluster-eroded single crystal diamond

Friction properties of cluster-eroded surfaces of synthetic single crystal diamond (Monodite) are compared after erosion with high-speed CO₂ cluster beams as well as with corresponding Ar cluster beams, the cluster impact kinetic energy being 100 keV in both cases. The respective friction values are determined by atomic force microscope measurements. Using CO₂ clusters, the reactive accelerated cluster erosion (RACE) of the single crystal diamond substrates leads to more than seven times higher friction values than those observed after erosion with non-reactive accelerated Ar clusters. Molecular dynamics calculations reveal related differences in the simulations of respective single cluster impacts already at 2 ps after impact.     

Linearer Stark-Effekt desR-Zentrums in LiF

The K-ionization cross section of Aluminium by electron impact was measured detecting quantitatively the Al-K X-rays emitted by thin targets of known mass thickness. The apparatus and the measurements are briefly described. The experimental results are considerably higher than the values of the theories using the Born approximation. The discrepancy increases with increasing energy of the incoming electron. At twenty-fold threshold energy for example, the measurements are higher thanBurhop's calculations by a factor of 1.7. It is shown that considering the process ofK-ionization the influence of the nuclear field on the impact electron increases with decreasing atomic number. Thus, the calculations ofRudge andSchwartz using coulomb wave functions for the impact electron, are closest to the measurements (maximum deviation 16%). The formula ofGryzinski based on classical calculations is a good approximation to the experimental results if multiplied by a factor 1.23.     

Theoretical study of small silicon clusters on a graphite layer

In a series of recent experiments, the HOMO-LUMO energy gaps of small Si clusters deposited on a graphite substrate have been determined by Scanning Tunneling Microscopy (STM). The values obtained were found to be substantially smaller than the energy gaps of corresponding passivated clusters. This work considers dimensional reduction as a possible mechanism for a sizeable energy gap narrowing by the example of the system Si₅. The impact of the graphite substrate on the deposited species is investigated in the framework of a pseudocluster model. Received 30 November 2000     

压力膨化处理对正极性聚丙烯蜂窝膜的驻极体性质的影响

压力膨化处理工艺能够显著改善聚丙烯蜂窝薄膜（cellular polypropylene） 驻极体的压 电活性.通过热脉冲技术、表面电位衰减测量及TSD 电流谱分析等研究了经恒压正电晕充电 的聚丙烯蜂窝膜的陷阱能级分布特征，讨论了压力膨化处理工艺对这类蜂窝膜驻极体电荷稳 定性及电荷输运特性的影响.结果说明，PP 蜂窝膜内存在着位于中能级区的能值各异的三种 分立陷阱，深能值陷阱和浅能值陷阱的大多数位于孔洞膜近表面的体层或体内，而中等能值 陷阱则主要位于自由面附近.压力膨化处理改变了PP 蜂窝膜的能阱状态并在一定程度上降低 了这类孔洞膜驻极体的电荷储存稳定性，但没有明显影响其由慢再俘获效应占主导地位的脱 阱电荷输运特性. 关键词： 压力膨化处理 聚丙烯蜂窝膜 驻极体 电荷储存与陷阱分布 电荷输运     

Pulsed ion beam parameters to ensure maximum coefficients of metal surface erosion

Erosion of metal surface under pulsed ion beams is investigated using a two-phase evaporation model. The coefficients of erosion due to evaporation are calculated for aluminum, iron and copper under irradiation by submicrosecond ion beams of carbon with the initial particle energy within the range 10–1000 keV. The ion energy and ion beam current density values of the most efficient erosive impact are determined. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 31–36, May, 2007.     

Excitation functions of Cd III 4d85s2 (Beutler) states by electron impact on Cd atoms

Emission cross sections for the lines from Cd III 4d⁸5s² (Beutler) states by single electron impact on Cd atoms have been measured in the electron energy region of 40–250 eV. The measured values are of the order of 10^-19 cm².