Charge and Energy Dependences of Ionization and Transfer for Helium in Collisions with Fast Charged Projectiles

The classical method within the independent electron model is employed to investigate （i） charge dependences of single and double ionization for helium by various charged ions A^q＋ （q = 1 - 8） at impact energies of 0.64 and 1.44 MeV/u, respectively, （ii） energy dependences of transfer ionization for helium by 0.5-3 MeV/u A^8.9＋ ions impact. The Lenz-Jensen model of the atom is applied instead of the Bohr model of the atom, and the impact-parameter dependences are also introduced into the calculations. Satisfactory agreement is found between theoretical and experimental data.     

低电荷态离子原子碰撞过程中的转移电离机理的研究

介绍了使用位置灵敏技术和飞行时间方法研究中低能低电荷态离子-原子碰撞过程中转移电离与单电子俘获过程.对于确定的入射离子电荷态,通过理论分析及与实验数据对比给出了转移电离与单电子俘获截面比R_TS随着入射离子速度V_P的变化规律和转移电离过程中电离的电子主要来自靶原子的最外亚壳层. 关键词： 转移电离 逃离半径 电离半径 俘获半径     

Classical Study of Transfer and Ionization in A^2＋＋He Collisions

A simple model for the direct ionization and transfer ionization probabilities in A^2＋＋He collisions in a wide projectile energy range is proposed based on the Bohr-Lindhard model and the classical statistical model. The calculated cross sections are in satisfactory agreement with the experimental data available.     

Single-and-double electron loss of O2+ in collisions with argon and helium

This paper reports that the ratios of double to single electron loss cross-section （R） of O^2＋ in collision with Ar and He at the velocity of 1 -4 vo（vo is the Bohr velocity） have been obtained by the coincidence technique. The trend of R - V in the experiment indicates that the effective charge varies with injected velocity. The effective charge can be obtained by the n-body classical trajectory Monte Carlo method, which is interpreted by the molecular Coulomb over barrier model.     

Investigation of transfer ionization in collisions of partially stripped carbon ions with helium at low to intermediate velocities

The ratios of transfer ionization (TI) to single-electron capture (SC) cross sections have been measured for the collisions of partially stripped C^q+ ions (q=1--4) with He. The collision velocity ranges from 0.7 to 4.4v₀ (v₀ is the Bohr velocity). The projectile-ion and recoil-ion coincidence technique is used to separate the processes of TI and SC. The ratios reach the maximum when the velocity is about 3.7v₀ This can be explained qualitatively based on the two-step mechanism. The experimental results are also compared with the results calculated using the classical trajectory Monte Carlo (CTMC) method. The CTMC results are in agreement with the experimental data basically. The discrepancies in higher velocity region are interpreted by the effective charge effect.     

Double Electron Processes in Collisions of Partially Stripped Ions C^q＋ （q = 1-4） with Helium

The multi-electron processes are investigated for 17.9-120 keV/u C^1＋, 30-323 keV/u C^2＋, 120-438 keV/u ^C3＋, 287-480 keV/u C^4＋ incident on a helium target. The cross-section ratios of double electron （DE） process to the total of the single electron （SE） and the double electron process （i.e. SE＋DE）, the direct double electron （DDI） to the direct single ionization （DSI） as well as the contributions of DDI to DE and of TI to DE are measured using coincidence techniques. The energy and charge state dependences of the measured cross-section ratios are studied and discussed.     

C3+与Ne碰撞过程纯电离绝对截面的测量和研究

介绍了离子-原子碰撞过程中双微分绝对截面的计算方法.利用符合技术测量了中能区C3++Ne碰撞系统的纯电离微分绝对截面.将实验结果与多体经典蒙特卡罗方法计算结果进行对比后发现,纯电离截面随入射能量变化的趋势基本一致,对理论与实验产生差异的原因作了分析.对多重电离的电离机制分析表明:高价态的反冲离子主要来自于俄歇贡献;随着入射能量的升高,电子-电子间的库仑作用也逐渐显现.此实验方法可以用于相同实验装置上的各种反应出射道的绝对截面测量,入射离子种类及入射离子能量范围将得到拓展.     

Production of recoil ions He^i＋ accompanied by single electron loss of 0.2-7 MeV C^q＋ and 0.25-5 MeV O^q＋ （q = 1- 4） ions

Target ionization accompanied with projectile electron loss is investigated for 0.2-7 MeV C^q＋ （q = 1 - 4） with He and 0.25-5 MeV O^q＋ （q = 1 - 4） with He collisions. For projectile single-electron loss channel, the He double-to-single ionization ratio R is nearly independent of projectile charge state but dependent on the nuclear charge of projectile Zp. The results are analysed with atomic structure qualitatively. So far there have not existed the experimental data comparable with our results, to our knowledge. The ratio R is interpreted in terms of the two-step mechanism. This analysis agrees well with similar experiments in the literature.     

中低能非全裸C离子与He原子的碰撞研究

采用反冲离子飞行时间-散射离子位置灵敏符合测量技术，测量了能量范围在0.7v₀—4.4v₀(v₀为玻尔速度)的碳离子C^q+(q=1—4)与He原子碰撞过程不同出射道靶原子的双电离与单电离截面比R，包括入射离子不损失电子(直接电离)的出射道(R_q,q),入射离子俘获一个电子的出射道(R_q,q-1)和入射离子损失一个电子的出射道(R_q,q+1)，并研究了R随入射C离子的能量及电荷态的变化关系.实验表明，对给定电荷态的入射离子，靶原子的双电离与单电离截面比R与出射道有很强的依赖关系，即R_q,q<R_q,q+1<R_q,q-1.直接电离出射道截面比R_q,q与入射离子电荷态几乎无关，而入射离子俘获一个电子的出射道和损失一个电子的出射道靶原子双电离与单电离截面比R_q,q-1和R_q,q+1却与入射离子电荷态有很强的关系.采用原子极化理论和电子屏蔽与反屏蔽作用对实验结果进行了解释. 关键词： 离子-原子碰撞 电离 截面比     

C3+与Ne碰撞过程纯电离绝对截面的测量和研究

介绍了离子-原子碰撞过程中双微分绝对截面的计算方法.利用符合技术测量了中能区C³⁺+Ne碰撞系统的纯电离微分绝对截面. 将实验结果与多体经典蒙特卡罗方法计算结果进行对比后发现，纯电离截面随入射能量变化的趋势基本一致，对理论与实验产生差异的原因作了分析. 对多重电离的电离机制分析表明：高价态的反冲离子主要来自于俄歇贡献；随着入射能量的升高，电子-电子间的库仑作用也逐渐显现. 此实验方法可以用于相同实验装置上的各种反应出射道的绝对截面测量，入射离子种类及入射离子能量范围将得到拓展. 关键词： 离子-原子碰撞 绝对截面 纯电离