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1.
The values of direct double- to-single ionization ratio R of helium atoms induced by C^q+, O^q+ (q = 1 -4) ions at incident energies from 0.2 to 8.5MeV are measured. Based on the existing model (Shao J X, Chen X M and Ding B W 2007 Phys. Rev. A 75 012701) the effective charge of the projectile is introduced to theoretically estimate the value of R for the partially stripped ions impacting on helium atoms. The results calculated from our "effective charge" model are in good agreement with the experimental data, and the dependence of the effective charge on the ionization energy of the projectile is also discussed qualitatively.  相似文献   

2.
In this paper a projectile ion-recoil ion coincidence technique is used to investigate the transfer ionization processes in collisions of 0.22-6.30 MeV C q+ ions and 0.25-6.35 MeV O q+ ions (q=1,2,3,4) with the He atom separately.The cross section ratio f of transfer ionization to single electron transfer is measured,and the dependence of f on both charge state q and energy E of the projectiles is investigated.The electron-structure and the mechanisms leading to transfer ionization affect the dependence of f on q and E.Our measurements,along with other data published previously,suggest a similar dependence of f on charge state and energy of projectile for partially stripped ions over a large energy range.The maximum value of f is approximately 0.17q 0.60 ;the energy corresponding to maximum f is about 160q 0.60 keV/u.  相似文献   

3.
The cross section ratios of the double, triple and quadruplicate ionization to the single ionization of argon by 1.5-7.5 MeV partially stripped carbon ions are measured by using time-of-flight technique. The Auger transition and the charge exchange process in the multiple ionization of argon are studied. The ratios of cross sections of the direct multiple ionization to those of the direct single ionization are obtained by subtracting the parts of the Auger transition and the charge exchange process from the measured data. It is found that the cross section ratios of the direct multiple ionization to those of the direct single ionization are in good agreement with the predicted mniti-step (ν/qeff)-2n+2 law.  相似文献   

4.
主要揭示了不同电离机制对高电荷态离子单电离和多重电离的贡献 ,包括直接电离 (一步过程 )、激发 自电离 (两步过程 )以及内壳Auger过程 ,研究了高电荷态镨离子的电子碰撞电离. Electron-impact ionization of ions is one of the most fundamental processes in every kind of plasma. Especially in high-temperature plasmas-whether in laboratory (nuclear fusion) or in astrophysics (atmosphere of stars)-atoms become ionized into multiply-charged ions by electron impact. The main purpose of our investigations is to unravel the contributions from different ionization mechanisms-like direct ionization (one-step process), excitation-autoionization (two-step process) and...  相似文献   

5.
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 4.4 vo (vo 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 3.7 vo. 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.  相似文献   

6.
本文利用经典过垒电离模型(Class Over Barrier Ionization)处理100-400ke V/amu强扰动区(q/v1)的不同价态非全裸离子Cq+(q=1-4)与全裸离子H1+,He2+,Li3+与He原子碰撞过程.发现相同价态下,全裸离子的双单电离截面比R21明显低于非全裸离子,原因在于两者的电子结构明显不同.非全裸离子的外壳层电子在碰撞过程中会有一定几率过垒,这在以往的研究中并未考虑.利用模型计算结果与实验数据的比对,估计入射离子第二有效电荷,最终确定入射离子在电离过程中的第一和第二有效电荷.  相似文献   

7.
在ECPSSR理论的基础上, 利用OBKN近似描述电子俘获过程, 得到了包括电子俘获过程贡献的ECPSSR理论, 编写了相应的计算程序。 采用该程序计算了不同电荷态离子与多种靶原子碰撞的电子俘获截面和相应的X 射线产生截面, 将计算得到的包含电子俘获过程贡献的X 射线产生截面与实验结果进行了比较。 对于具有满K壳层的入射离子碰撞, X 射线产生截面与入射离子电荷态基本无关; 对于以直接电离为主导的碰撞过程, 计算得到的X 射线产生截面与实验数据符合得很好; 对于全裸和单K空穴入射离子的碰撞, 计算高估了X 射线产生截面。 Based on the ECPSSR theory, the contribution of the electron capture is described by the OBKN theory. The cross sections of electron capture and X ray production for the collision of different charge state projectiles with various targets are calculated, and compared with the available experimental data. It is found that the obtained X ray production cross sections are almost independent of the projectile charge states for projectiles without a K vacancy. For the collision processes of direct ionization, the present calculated results agree well with the experimental data. The calculations overestimate the X ray production cross sections for the projectiles with full and a K vacancy.  相似文献   

8.
Slow Ar recoil ion Production cross sections by 42 MeV Ar^1 (q=4-14) projectiles were measured using a projectile ion-recoilion coincidence technique in order to provide information on mechanisms of multiple ionization of target atome through pure ionization as well as of that accompaied simultaneously with multiple electron loss or capture of projectiles.The present results suggest that inner-shell electron processes caused through electron transfer into projectiles and also electron ionization by projectiles play a key role in the production of multiply charged recoil ions.  相似文献   

9.
Slow Ar recoil ion production cross sections by 42MeV Ar~(q )(q=4-14)projectiles were measured using a projectile ion-recoilion coincidence technique in order to provide information onmechanisms of multiple ionization of target atoms through pureionization as well as of that accompanied simultaneously with mul-tiple electron loss or capture of projectiles. The present resultssuggest that inner-shell electron processes caused through electrontransfer into projectiles and also electron ionization by projectilesplay a key role in the production of multiply charged recoil ions.  相似文献   

10.
Fe K-shell ionization cross sections induced by 2.4–6.0 MeV Xe20+are measured and compared with different binaryencounter-approximation(BEA)models.The results indicate that the BEA model corrected both by the Coulomb repulsion and by the effective nuclear charge(Zeff)agrees well with the experimental data.Comparison of Fe K-shell X-ray emission induced by 5 MeV xenon ions with different initial charge states(20+,22+,26+,30+)verifies the applicability of the effective nuclear charge(Zeff)correction for the BEA model.It is found that Zeffcorrection is reasonable to describe direct ionization induced by xenon ions with no initial M-shell vacancies.However,when the M shell is opened,the Zeffcorrected BEA model is unable to explain the inner-shell ionization,and the electron transfer by molecular-orbital promotion should be considered.  相似文献   

11.
The double and single ionization cross section ratios of helium by partially stripped carbon, oxygen and fluorine ions are measured for projectile charge states ranging from +1 to +4 and impact energies from 1.5 MeV to 7.5 MeV. The effective charge effect in partially stripped ion-helium collisions is studied. It is found that the effective charge qeff increases as the impinging energy increases and q eff shows a modest dependence upon the projectile charge state in the present energy range. The projectile charge state, projectile energy, projectile and target electronic state dependences of the effective charge effect may be explained using orbital interpenetrating.  相似文献   

12.
The double and single ionization cross section ratios of helium by partially stripped carbon, oxygen and fluorine ions are measured for projectile charge states ranging from +1 to +4 and impact energies from 1.5 MeV to 7.5 MeV. The effective charge effect in partially stripped ion-helium collisions is studied. It is found that the effective chargeq eff increases as the impinging energy increases andq eff shows a modest dependence upon the projectile charge state in the present energy range. The projectile charge state, projectile energy, projectile and target electronic state dependences of the effective charge effect may be explained using orbital interpenetrating.  相似文献   

13.
采用飞行时间符合技术测得1.5—7.5MeV非全裸碳离子轰击氦原子,引起氦原子双重电离与单重电离的相对截面比。对碰撞过程进行多体经典轨道蒙特卡罗模拟,得到相应的Olson—Schlachter曲线,结合本实验结果,给出非全裸碳离子引起氦原子双重电离和单重电离的绝对截面,并进行了讨论。  相似文献   

14.
A nonperturbative method is developed for the calculation of cross sections of inelastic processes in collisions between structured high-charge heavy ions moving at relativistic velocities and atoms. By structure ions are meant partly stripped ions consisting of an ion nucleus and a number of bound electrons which partly compensate the core charge and form the electron “coat” of the ion. The single ionization cross section of hydrogen atom and single and double ionization cross sections of helium atom are calculated. It is demonstrated that the inclusion of the extent of ion charge may bring about a marked variation of the respective cross sections compared to ionization by point ions of the same charge and energy.  相似文献   

15.
利用2~8 MeV的Naq+、Clq+(q=2,3,4,5)轰击氦原子,对碰撞的直接多重电离过程进行研究.实验采用反冲离子-散射离子飞行时间符合技术,通过反冲离子飞行时间谱区分不同价态反冲离子;利用静电偏转和位置灵敏探测技术区分不同电荷态散射离子;结合CAMAC-PC多参数获取系统得到一定价态散射离子所对应的反冲离子电荷态分布谱;经分析该谱得到直接多重电离截面与直接单电离截面之比R21.讨论了R21随入射离子速度和电荷态的变化关系.  相似文献   

16.
In this paper a projectile ions recoil ions coincidence technique is employed to investigate the target ionization and projectile charge state changing processes in the collision of 0.22-6.35 MeV Cq^+ (q = 1 - 4) ions with argon atoms. The partial cross section ratios of the double, triple, quadruplicate ionization to the single ionization (or the single capture) of argon associated with single electron loss (or single electron capture) by the projectile are measured and compared with the previous experimental results. In the present experiment, it is observed that the ratios of ionization cross sections R associated with single loss and single capture depend strongly on the projectile charge state and vary significantly with different reaction channels as impact energy increases. In addition, this paper gets empirical scaling laws for the ionization cross section ratios R corresponding to the projectile single loss and finds that the ratios of the double ionization to the single ionization associated with single electron capture remain constant in the present energy range.  相似文献   

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