H+5团簇离子及其中性团簇产物H3和H4

报道了H⁺₅的实验结果.分析讨论了H⁺₅的 形成和分解途径.根据理论分析，以稳定的H⁺₃为核心与一个或多个氢分子结合可能形成稳定的H^{+_n氢团簇离子.另一方面，在高频离子源中, 有发生H+₃与H₂反应的条件.实 验中，从高频离子源引出的离子束被静电加速器加速，然后用9 关键词： +}₅团簇离子')" href="#">H⁺₅团簇离子 3中性团簇')" href="#">H₃中性团簇 4中性团簇')" href="#">H_{4中性团簇}     

Dissociative charge exchange in collisions of 10keV H 2 + ions on H2, He,and Ar targets

The velocity distributions of H-H fragment pairs arising from dissociative collisions of 10keV H ₂ ⁺ ions incident on H₂, He, and Ar were measured using a flight-time-difference method. The H ₂ ⁺ ions were produced in an electron impact ion source at two different electron energies, at 100eV and 18eV. The influence of the electron energy on the fragment velocity distributions is studied. Conclusions are drawn on the processes which lead to the formation of neutral fragment pairs. Electron capture into the repulsive b³ Σ _u ⁺ state of H₂ plays a dominant role.     

Fragmentation of polyatomic ions produced by electron-loss collisions of butane and isobutane molecules with ions of kiloelectronvolt energy

Fragmentation accompanying the loss of electrons by butane and isobutane (C₄H₁₀) molecules in collisions with energy H⁺, He²⁺, and Ar⁶⁺ ions of kiloelectronvolt energies is studied. The electron density functional technique is applied to C _n H_2n+2 alkane molecules and their respective C _n H _2n+2 ⁺ ions to carry out quantum-chemical calculations of the atomic spacing, electron total energy for the initial configuration of the ionizing molecules and ions in the ground state, and atomic bond breaking energy necessary to produce different ion fragments. The fragmentation energy is correlated with the fragmentation probability. It is shown that the relative cross sections of ion fragmentation depend primarily on the related energy consumption. However, the process cross section is also strongly affected by the initial configuration of C₄H₁₀ isomer molecules, as well as by the amount of dangling and arising atomic bonds involved in the formation of each ion fragment.     

Study of the luminescence of H2O and D2O ices induced by charged-particle bombardment

We measured the optical emission of H₂O and D₂O ices in visible region (300-500 nm) induced by energetic hydrogen ions (H⁺, H₂⁺, and H₃⁺) irradiation. Our analysis of the data of ion-stimulated luminescence (ISL) shows that all spectra of ISL emission are identical, independent of projectile. We show that all lines in the ISL emission spectrum may be assigned to decays from excited particles and/or fragments of H, H₂, OH, and H₂O. From the independence of emission spectrum on projectile we conclude that the final process causing the emissions may be attributed to the interaction between H⁺ (and/or H) and the water molecules.     

Molecular effects in ion-induced secondary electron spectra

The energy spectra of slow secondary electrons from a copper surface under bombardment with H⁺, H⁺₂, and H⁺₃ ions have been measured at an energy of 200 keV/atom. Distinct molecular effects are revealed in the ratios of the respective distribution curves for molecular ion and proton impact.     

Secondary ion emission under the bombardment of Si by multiply charged Si q+ ions

The spectra of secondary ion emission under the bombardment of a B-doped Si target by multiply charged Si ^q+ ions (q = 1?C5) have been studied in the energy range of 1 to 10 keV per unit of charge. A multifold increase in the yield of secondary cluster Sk _n ⁺ ions, multiply charged Si ^q/+ ion (q = 1?C3), and H⁺, C⁺, B⁺, Si₂N⁺, Si₂O⁺ is observed as the charge of the multiply charged ions increases. The increase in the yield of secondary ions with increasing charge of the multiply charged-ion charge is most significant for ions with relatively high ionization potentials.     

Dissociation of alkane ionized molecules

The subject of investigation is the fragmentation of variously charged molecular ions arising in col-lisions of several kiloelectronvolt H⁺, He²⁺, and Ar⁶⁺ ions with molecules of the simplest alkanes (from methane to butane). Using the method of time-of-flight mass spectrometry, the formation cross sections of dissociation-induced fragment ions are measured. The dissociation takes place when an incident ion captures an electron from a methane, ethane, or propane molecule. The role of additional ionization of the molecule, which accompanies the electron capture by the incident ion, is elucidated. The kinetic energy spectrum for protons resulting from the fragmentation of multiply charged alkane ions is determined. The most plausible kinetic energies of protons depending on the degree of ionization and molecule size fall into the range 1–25 eV. It is shown that, when the molecule loses several electrons, the kinetic energies of protons are governed by Coulomb interaction between all fragment ions and are determined by their flying apart from the relative spatial arrangement of corresponding atoms in a parent molecule.     

Features of the variation in reflection spectra of the F4MB/Al coating under bombardment by H+, H 2 + and H 3 + ions

Variations of reflection spectra for the F4MB/Al coating, based on fluoroplastic film, occurring under bombardment by H⁺, H ₂ ⁺ , and H ₃ ⁺ , ions with energy 15 keV are investigated. It is established that the variations in the reflection spectra and integrated absorption coefficient are not proportional to the mass of the hydrogen ion and obey the different regularities depending on the energy of the absorption band.     

MeV氢微团簇离子与固体介质的电荷交换

利用静电加速器提供的0.6—1.8MeV的H⁺，H⁺₂，H⁺₃离子，轰击不同厚度的碳膜，分别测量这些离子通过碳膜后各种产物的产额. 得到了不同能量的H⁺通过碳膜后中性原子H和负离子H^-的产额随入射质子速度的变化关系；分别得到能量为1.2MeV,1.8MeV的H⁺₂，H⁺₃团簇离子通过不同厚度碳膜的透射产额及其与团簇离子在碳膜中驻留时间的关系；对结果进行了理论分析与讨论. 关键词： 团簇离子 电荷交换     

Neutral beam sputtering of positive ion clusters from alkali halides

Neutral argon atom beams of 15 keV energy have been used to sputter alkali halides and the ejected positive ions have been analysed in energy, mass and angular distribution.

The use of a neutral beam, rather than an ion beam, minimizes surface charge and the deflection of ejected ions by electrostatic interaction with a charged incident beam.

A cluster component of the form K₂Cl⁺, K₃Cl⁺ ₂ and higher members of the series is found for all alkali halides studied.     

A translational energy spectrometer to probe interatomic potentials: Dissociation dynamics of CO2 + ions

A new ion translational energy spectrometer has been developed to carry out low-energy, gas-phase ion-molecule collision experiments which aim to probe molecular potential energy surfaces. The collisional technique employed relates small changes in the kinetic energy of a projectile ion after it has undergone collision with a static neutral atom/molecule to changes in the overall potential energy of the collision system; information can be furnished about the interaction potential between the projectile and the target. First measurements are reported of a high resolution target excitation spectrum obtained in 1.8 keV collisions of H₂ ⁺ ions with N₂. New results pertaining to collision-induced dissociation of CO₂ ⁺ ions are presented and discussed in terms of potential functions of low-lying electronic states of the molecular ion.     

Observation of high-energy electrons from a metal target irradiated by protons with a mean energy of 25 keV

Electrons with abnormally high energies of up to 16 keV are detected from an iron target irradiated by ions (H⁺, Fe⁺, Fe²⁺, Fe³⁺) with energies ranging from 20 to 100 keV from the plasma of a high-power femtosecond laser pulse with an intensity of 10¹⁶ J/(s cm²). These electrons indicate that the energy of an incident ion is almost completely transferred to an electron knocked out of the target. In a range of 6–16 keV, the spectrum of electrons knocked out of the K shell of iron atoms by protons with an energy of 22 ± 2 keV is quasi-exponential with an exponent of 4 keV. For 8-keV electrons, the double differential cross section for ionization by such protons is estimated as 10^?7 b/(eV sr).     

化合物和合金中离子投影射程分布矩的计算(Ⅱ)——轻离子(Z1≤10)的射程分布矩

本文根据离子在固体材料中电子阻止截面的实验资料,给出了低能Li⁺,Be⁺,B⁺,C⁺,N⁺,O⁺,F⁺,Ne⁺等离子在固体中电子阻止截面S_e的经验公式。这些经验公式既能够很好地反映电子阻止本领的Z₁和Z₂振荡、又能正确地给出S_e随离子能量E的变化关系。用这种以实验为基础的S_e经验公式和符合于WHB势的核散射函数,计数了从H⁺到Ne⁺十种轻离子在非晶Al₂O₃,SiO₂,20/25/Nb不锈钢,LiNbO₃和UO₂等材料中的投影射程分布的一次至三次矩。将计算值与近几年的实验测量及其他人的计算结果进行了比较,在低能端,我们计算的平均投影射程R_p与实验符合得更好。 关键词：     

1,4-二氧六环的真空紫外同步辐射光解离电离研究

The photoionization and photodissociation of 1,4-dioxane have been investigated with a reflectron time-of-flight photoionization mass spectrometry and a tunable vacuum ultraviolet synchrotron radiation in the energy region of 8.0-15.5 eV. Parent ion and fragment ions at m/z 88, 87, 58, 57, 45, 44, 43, 41, 31, 30, 29, 28 and 15 are detected under supersonic conditions. The ionization energy of DX as well as the appearance energies of its fragment ions C₄H₇O₂⁺, C₃H₆O⁺, C₃H₅O⁺, C₂H₅O⁺, C₂H₄O⁺, C₂H₃O⁺, C₃H₅⁺, CH₃O⁺, C₂H₆⁺, C₂H₅⁺/CHO⁺, C₂H₄⁺ and CH₃⁺ was determined from their photoionization efficiency curves. The optimized structures for the neutrals, cations, transition states and intermediates related to photodissociation of DX are characterized at the B3LYP/6-31+G(d,p) level and their energies are obtained by G3B3 method. Possible dissociative channels of the DX are proposed based on comparison of experimental AE values and theoretical predicted ones. Intramolecular hydrogen migrations are found to be the dominant processes in most of the fragmentation pathways of 1,4-dioxane.     

Relative Anfangsbesetzungszahlen der Zustände 2p und 3d folienangeregter Wasserstoffatome

The Lyman-α radiation of fast moving hydrogen atoms excited by a thin carbon foil is measured using a channel electron multiplier with a Mg F₂ filter. The photonintensity-versus-distance curve exhibits the 2p (1.596 ns) decay followed by a cascade tail originating mainly from the 3d level (15.47 ns). The data is analyzed by a computer program using the known mean lives of the 2p, 3d, and 3s states and yields the relative initial state populationY=N _2p ⁰ N _{3 d} ⁰ which depends on the kind of incident ions (H⁺ or H₂ ⁺). For H₂ ⁺ ions, excited with a single foil, there might be a slight dependence ofY on the beam velocity, but for H⁺ ions incident on the foil, no such dependence is found.     

Spectre de photoélectrons et calcul des facteurs de franck-condon pour H2O,D2O,HDO

The first band of the photoelectron spectrum of HDO has been recorded. In agreement with the selection rules of the group theory, the fundamental terms of the three symmetric vibrations of HDO (C_s symmetry) have been observed. Taking the geometry of the ion as parameters, the Franck-Condon factors for the ionization of H₂O, D₂O and HDO have been calculated. The geometry of the H₂O⁺, D₂O⁺, HDO⁺ ions (ground state) have been determined accurately by comparison of the calculated results with the corresponding photoelectron spectra. This geometry is approximately the same for the three ions: r_OH  1,00 Å and < HOH  110°.     

Field-Induced and Surface-Catalyzed Formation of N2H Ions

Using H₂-N₂ mixed gases, high-electric-field-induced formation of ions such as N₂ ⁺ and N₂H⁺ on a surface of gold has been investigated in the pulsed-laser time-of-flight atom-probe field ion microscope. The N₂H⁺ ions are found from the lattice steps of the surface in the range (30-40) V/nm. The formation of the ions depends not only on the applied field strength, but also on the atomic structure of the substrate. By applying theoretical values of the binding energy and ionization potentials of N₂H, as calculated by the ab initio method and using measurements of the energy distributions of the N₂ ⁺ and N₂H⁺ ions, several conclusions can be drawn.     

Formation of bubbles and blisters in hydrogen ion implanted polycrystalline tungsten

ABSTRACT

Tungsten (W) has been regarded as one of the most promising plasma facing materials (PFMs) in fusion reactors. The formation of bubbles and blisters during hydrogen (H) irradiation will affect the properties of W. The dependence of implantation conditions, such as fluence and energy, is therefore of great interest. In this work, polycrystalline tungsten samples were separated into two groups for study. The thick samples were implanted by 18?keV H₃⁺ ions to fluences of 1?×?10¹⁸, 1?×?10¹⁹ and 1?×?10²⁰ H⁺/cm², respectively. Another thick sample was also implanted by 80?keV H₂⁺ ions to a fluence of 2?×?10¹⁷ H⁺/cm² for comparison. Moreover, the thin samples were implanted by 18?keV H₃⁺ ions to fluences of 9.38?×?10¹⁶, 1.88?×?10¹⁷ and 5.63?×?10¹⁷ H⁺/cm², respectively. Focused ion beam (FIB) combined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for micro-structure analysis, while time-of-flight ion mass spectrometry (ToF-SIMS) was used to characterize the H depth profile. It is indicated that bubbles and blisters could form successively with increasing H⁺ fluence. H bubbles are formed at a fluence of ～5.63?×?10¹⁷ H⁺/cm², and H blisters are formed at ～1?×?10¹⁹ H⁺/cm² for 18?keV H₃⁺ implantation. On the other hand, 80?keV H₂⁺ ions can create more trapping sites in a shallow projected range, and thus enhancing the blisters formation with a relatively lower fluence of 2?×?10^17?H⁺/cm². The crack-like microstructures beneath the blisters are also observed and prefer to form on the deep side of the implanted range.     

Secondary ion emission from Si under nitrogen ion bombardment

The yield and energy distribution of positive secondary ions emitted from Si under N₂⁺ ion bombardment were measured. The obtained mass peaks correspond to three types of secondary ion species, that is, physically sputtered ions (Si⁺, Si₂⁺), chemically sputtered ions (SiN⁺ Si₂N⁺) and doubly charged ions (Si²⁺). The dependence of secondary ion emission on the primary ion energy was studied in a range of 2.0–20.0 keV. The yields of physically and chemically sputtered ions were almost independent of the primary ion energy. The yield of the doubly charged ion strongly depended on the primary ion energy. The energy distribution of secondary ions of the three types showed the same dependence on the primary ion energy. The most probable energy of the distribution increased with the primary ion energy. On the other hand, for the energy distribution curves of sputtered ions, the tail factors N in E^?N were constant and showed a m/e dependence.     

Angular dependent photon-stimulated desorption of ions from a V2O5(010) surface

Using a display-type analyzer, we have measured the angular and energy distribution of O⁺ ions desorbed from a V₂O₅(010) surface by incident photons. The desorbed ions were mass-analyzed using time-of-flight gating techniques. The angular distribution of desorbed ions was found to be strongly peaked in the direction of the surface normal. This strongly directional desorption pattern reflects the local bonding geometry of the topmost oxygen atoms in the surface. The observed photoexcitation spectrum of the ion yiel can be explained with the core level Auger decay model formulated by Knotek and Feibelman.