低速多电荷态离子He2+、O2+和Ne2+与W靶表面

本文报道了He2+,O2+和Ne2+与W靶表面相互作用中的动能电子产额随离子入射速度变化的实验测量结果.结果表明：在本实验的入射速度范围内,对同一入射离子,动能电子产额随入射离子的速度增大而线性增加.基于动能电子发射的机理,我们分析了影响动能电子产额的因素,理论上得出动能电子产额与入射速度增长呈线性增加的关系,取得了实验上和理论上一致的结果.     

高电荷态离子207Pb36+与金属Nb表面作用产生的二次离子产额

本文报道了利用兰州重离子加速器国家实验室ECR源引出的高电荷态离子207Pb36+入射到金属Nb表面产生二次离子溅射的实验测量结果.实验发现,二次离子产额Y随入射初动能Ek的增加有先增加后减小的关系,二次离子产额有一个峰值.理论分析认为,这一过程是势能沉积作用与线性级联碰撞过程协同作用的结果.     

129Xeq+轰击N型和P型Si表面时的电子发射产额研究

在兰州重离子加速器国家实验室测量了1.8 MeV Xeq+离子分别轰击N型和P型Si两种靶材表面时的电子发射产额。实验中,通过改变入射离子的电荷态,研究了入射离子势能沉积对两种靶材表面电子发射产额的贡献。结果发现同一离子入射时,N型Si表面的电子发射产额高出P型Si表面的电子发射产额约12.5%;对于具有相同入射动能的Xeq+离子,两种靶材表面的电子发射产额均随着入射离子势能的增加而线性增加。此外,还测量了3.4 MeV Xeq+离子分别轰击以上两种靶材时的电子发射产额,得到了类似的结果。本文利用功函数分别从动能电子发射和势能电子发射两个角度对实验结果进行了分析讨论。The electron emissions from N-type Si and P-type Si induced by 1.8 MeV 129Xeq+are measured in the National Laboratory of Heavy Ion Research Facility in Lanzhou,The contribution to electron emission yield from potential energy of incident ions is studied through changing the charge state of incident ions.The results show that for the same incident ion,electron emission yield of N type Si surface is higher than that of P-type Si surface about 12.5%.For incident ions with the same kinetic energy,both electron emission yields of two targets increase linearly with incident ion energy.In addition,the electron emissions induced by 3.4 MeV 129Xeq+from N-type Si and P-type Si mentioned above are measured,which give similar results.The experimental results are analyzed and discussed using work function from two angles of the kinetic electron emission and the potential energy electron emission.     

反冲原子对低速离子轰击Si表面时电子发射产额的影响

在兰州重离子加速器国家实验室电子回旋共振离子源高电荷态原子物理实验平台上,用低能(0.75keV/u≤EP/MP≤10.5keV/u,即3.8×105m/s≤vP≤1.42×106m/s)He2+,O2+和Ne2+离子束正入射到自清洁Si表面时二次电子发射产额的实验结果.结果表明电子发射产额γ近似正比于入射离子动能EP/MP.在相同动能下,γ(O)γ(Ne)γ(He),对于原子序数ZP比较大的O2+和Ne2+离子,ZP大者反而γ小,这与较高入射能量时的结果截然不同.通过计算不同入射能量下入射离子的阻止能损S,发现反冲原子对激发二次电子的作用随入射离子能量的降低显著增大,这正是导致在较低能量范围内二次电子发射产额与较高入射能量时存在差异的主要原因.     

近玻尔速度Ne2+离子穿过碳膜引起的电子发射

本文测量了入射能为2–25 keV/u的Ne²⁺离子穿过不同厚度碳膜诱导的前向、后向 (分别对应出射表面和入射表面) 电子发射产额. 实验中通过改变炮弹离子的能量, 系统的研究了势能沉积、电子能损以及反冲原子对前向、后向电子发射产额的贡献. 结果表明, 离子的势能沉积只对后向电子发射有贡献, 前向、后向电子发射产额分别与Ne²⁺离子在薄膜出射、入射表面的电子能损近似成正比关系, 其中电子能损很低 (对应于离子能量很低) 的时候, 反冲原子对电子发射的贡献不能忽略. 关键词： 近玻尔速度 电子发射 电子能损 反冲原子     

O~(2+)离子穿过碳膜引起的前后表面电子发射

测量了入射能为1.9~11.3 keV/u的O~(2+)离子穿过碳膜诱导的前向、后向(分别对应出射表面和入射表面)电子发射产额。实验中,通过改变入射离子的能量和流强,系统地研究了电子能损和离子束流强度对前向、后向电子发射产额的影响。结果表明,在本实验的能量范围内,前向、后向电子发射产额与对应表面的电子能损有近似的正比关系,而与束流强度无关。分析还发现引起后向电子发射的动能阈值约为0.2 keV/u,势能电子发射产额约为1 e~-/ion。     

50~250 keV质子入射SiC和Si靶时的电子发射特性研究

在中国科学院近代物理研究所兰州重离子加速器国家实验室测量了能量范围为50~250 keV 的质子入射碳化硅靶和硅靶表面的电子发射产额。实验结果发现,两种半导体靶材的电子发射产额随质子入射能量变化趋势均与作用过程中电子能损随质子入射能量的变化趋势相似。通过分析电子发射的能量来源,发现实验中电子发射产额主要由动能电子发射产额贡献,势能电子发射产额可以忽略不计。两种靶材的电子发射产额均近似地正比于质子入射靶材过程中的电子能损,比例系数B随入射能量略有变化。     

Ar16+和Ar17+离子与Zr作用产生的X射线谱

将超导离子源提供的10-20keV/q Ar16 和Ar17 离子入射到Zr金属表面,在相互作用中产生的X射线谱表明,高电荷态Ar16 离子在金属表面中性化过程中有可能存在多电子激发,使Ar16 的K壳层电子被激发形成空穴,在退激过程中发射特征Kα-X射线.空心原子Ar的K层发射X射线强度随入射离子的动能而减弱,靶原子Zr的L壳层发射X射线强度随入射离子动能的增加而增强.Ar17 的单离子的Kα-X射线产额比Ar16 单离子的Kα-X射线产额大5个数量级.     

高电荷态离子207Pb36+与金属Nb表面作用产生的二次离子产额

本文报道了利用兰州重离子加速器国家实验室的ECR离子源引出的高电荷态离子207Pb36 入射到金属Nb表面产生的二次离子的实验测量结果.实验发现,二次离子产额Y随入射初动能Ek的增加有先增加后减小的关系,在初动能为576 keV时二次离子产额达到最大.通过对实验点做高斯拟合发现,曲线峰值对应的入射初动能为602 keV.分析表明,这是势能沉积作用与线性级联碰撞过程协同作用的结果.高电荷态离子本身携带的高势能沉积在靶表面引起势能溅射,促进了二次离子的发射;而主导二次离子溅射的过程是动能溅射,它与靶表面的动量沉积(核能损)过程密切相关.     

高电荷态离子^207Pb^36＋与金属Nb表面作用产生的二次离子产额

本文报道了利用兰州重离子加速器国家实验室ECR源引出的高电荷态离子^207Pb^36＋入射到金属Nb表面产生二次离子溅射的实验测量结果，实验发现。二次离子产额Y随入射初动能B的增加有先增加后减小的关系，二次离子产额有一个峰值。理论分析认为，这一过程是势能沉积作用与线性级联碰撞过程协同作用的结果。     

Quartet states of He+ 2

The low lying quartet spectrum of the molecular helium cation is investigated by configuration interaction calculations. Using large Gaussian basis sets, potential energy curves for n ⁴Σ⁺ _u,g and n ⁴Π_u,g are computed for the states n = 1,…, 5. Several of these states lead to equilibrium configurations having rather extended bond lengths and some of them also a relatively large dissociation energy. The spectroscopic properties of these equilibrium configurations are studied. Quartet He⁺ ₂ is most strongly bound in its lowest state 1 ⁴Σ_u with R _e = 3.424 Å and D _e = 1.348 eV.     

Some bound states for the He2 2+ ion

Accurate potential energy curves for the lowest excited state of ¹Σ _g ⁺ symmetry and for the lowest state of ¹Σ _u ⁺ symmetry have been determined for the He₂ ²⁺ ion. The most flexible variational wavefunction used contained 153 linear and two non-linear parameters. The basis functions explicitly included interelectronic dependence and were constructed so that they led to the correct form for the dissociation products. The results are considered to be more accurate than those hitherto published. As well, and for the first time, the rovibronic energies for the two states were calculated.     

Chemiluminescent GeCl4 + O2 + Ar/He/Reactions

A chemiluminescent flame was produced in the reaction between GeCl₄ and an excited mixture of argon or helium with oxygen. Spectra of the reaction products were recorded and studied. Relative populations of the products in analyzed electronic, vibrational and rotational states corresponded to different temperatures.     

He + H2+反应的含时量子波包法研究

基于多体项展式的分析势能函数[1],用三雏含时量子波包法对He H2 进行了准确的动力学计算.计算的结果表明在一定的能量范围内增加入射原子的平动能及振动量子数对该反应具有促进作用;而增加转动量子数不利于反应的进行,同时也计算了该反应的反应截面和速率常数.     

Luminescent collisions of He+ and He++ ions with H2 molecules at energies below 2 keV

Spectroscopic studies of collisions between He⁺ and He⁺⁺ ions with H₂ gas target have been performed in the 200–600 nm wavelength range. Atomic lines of hydrogen Balmer series and several helium lines were identified and their excitation functions between 50 eV and 1 keV (2 keV for He⁺⁺) were determined.     

A comparative nearside-farside analysis of the He–N2 + and He–N2 inelastic collisions

A comparative study of the inelastic scattering of ¹⁴N₂ ⁺ and ¹⁴N₂ in collision with ³He atoms is presented. The unrestricted nearside-farside (NF) method proposed by Connor [J. Chem. Phys. 104, 2297 (1995)] is applied to analyse the Close Coupling rotationally state selected angular distributions for four kinetic energies. These four energies illustrate different regimes of the dynamics. The relationships between the structures of the calculated differential cross-sections (DCS) and the different regions of the potential energy surfaces involved which can be extracted from semi classical models are here easily obtained from a simple reading of the (NF) figures. At the higher energy far-off the wells (1000 cm^-1) the shape of the DCS are quite similar for the two systems and their nearside-farside components also, showing that the inelastic process is controlled by the short range repulsive part of the potential which is essentially the same for these two collisions. When the energy is decreased the differences between the two wells associated with the He–N₂ ⁺ and He–N₂ complexes are responsible for the differences between the DCS for the two systems. The farside component associated with the well become more and more prominent for the elastic scattering while inelastic scattering remains controlled by the repulsive core in a large angular interval. The nearside farside analysis gives also a new picture of a resonance which is regarded as an equilibrium between the repulsive and the attractive parts of the potential.     

Zeeman relaxation of N2 + (2Σ+) in collisions with 3He and 4He

We compare the cross sections for the transitions changing the projection of the total angular momentum of N₂ ⁺(²Σ) in collisions with ³He and ⁴He at very low collision energy. The fundamental states of the two nuclear spin isomers of N₂ ⁺ are considered as well as the two fine structure levels of the first excited para level N=2. It is shown that the two fundamental states of the two nuclear spin isomers behave differently. For the fundamental para level N=0 of N₂ ⁺, the projection changing cross section is always negligible compared to the elastic one for both He isotopes. For the fundamental ortho level N=1 of N₂ ⁺, the spin-rotation interaction couples the different spin levels directly so the spin relaxation becomes a first order process. The associated resonances increase the projection changing cross section which remains smaller but becomes comparable with the elastic one. This is in contrast with the excited rotational levels of N₂ ⁺, which for the rotational deactivation and elastic channels are found to be equal around the resonances for the collisions involving ³He. These two channels are always larger than the projection changing one. We also find that, for transitions involving the fundamental rotational state, the domain of validity of the threshold laws discussed by Krems and Dalgarno [Phys. Rev. A 67, 050704 (2003)] for a potential decreasing faster than 1/r2 is shortened, due to the long range charge induced dipole potential. This effect is illustrated for the collisions of ³He with the fundamental para state of N₂ ⁺.