7.0MeV的Xe30+入射Au靶引起Xe L、M壳层电子的多重激发简

探测了7.0MeV动能的129 Xe30+离子入射Au靶激发的Xe L-X射线谱.研究了Xe L、M壳层空穴的形成机制及Xe的M、N、O壳层伴存空穴对L-X射线能量与半高宽的影响.结果表明,由于大量伴线的产生,Xe的Lα、Lβ、Lβ2,15、Lγ1-X射线峰中心能量与无伴线的文献数据相比变大,峰的半高宽相对探测器的分辨率出现不同程度的增宽.     

碳离子碰撞引起的金L壳层X射线产生截面的实验研究 （原子分子会议文稿）

实验测量了20-50MeV的C离子和Au原子碰撞中Au产生的L 壳层X射线,研究了Au的L各支壳层产生截面的比值σ（Ll）/σ(Lα) 、σ（Lβ）/σ(Lα)、σ（Lγ）/σ(Lα)和总截面的比值σ（Ltotal）/σ(Lα)并将其绘制成与入射离子能量的关系图。利用L壳层的辐射跃迁几率,Croster-Kroning跃迁率和L亚壳层的荧光产额将平面波波恩近似（PWBA）和ECSSR理论计算的电离截面转换为L层X射线产生截面,并与实验结果相比较,结果表明σ（Ll）/σ(Lα) 、σ（Lγ）/σ(Lα)和总截面的比值σ（Ltotal）/σ(Lα)与ECSSR理论预测结果吻合得比较好,σ（Lβ）/σ(Lα)比两种理论预测的值偏小。     

不同离子激发Au靶的多电离效应

重离子与固体表面相互作用时,会引起靶原子内壳层的电离,相应空穴退激过程中发射的X射线对研究重离子与固体表面的相互作用有着重要意义,可为相关研究提供基础数据.目前,在K和L壳层电离方面做了一些工作,而M壳层的研究较少,本文依托兰州重离子加速器国家实验室320 kV高电荷态离子综合研究平台,测量了不同能量的H~+, Ar~(8+), Ar~(12+), Kr~(13+)和Eu~(20+)离子与Au表面作用产生的特征X射线谱及其能移,计算了X射线的产额比值.结果表明:重离子引起了靶原子内壳层的多电离,多电离效应使Au的MX射线有不同程度的能移;多电离程度取决于入射离子能量、离子的原子序数和其外壳层的空穴数量.     

洞态Ar原子K_α和K_β伴线和超伴线的理论计算

基于全相对论多组态Dirac-Fock方法,对L壳层旁观空穴下Ar原子退激衰变辐射K-X射线K_(α1,2)(K→L_(3,2))和K_(β1,3)(K→M_(3,2))的6908条伴线和超伴线跃迁能、跃迁概率进行了系统计算,计算结果与文献已有数据比较具有很好的一致性.通过对(K~(-1)L~(-1),l=0-8)伴线和(K~(-2)L~(-l),l=0-8)超伴线跃迁谱线卷积得了其合成谱,给出了L壳层不同空穴数下K-X射线伴线和超伴线的平均能量和平均跃迁强度.结果表明,退激辐射X射线能量以及能移与L壳层空穴个数呈现明显的线性关系.基于结论,进一步给出了跃迁能移与L壳层空穴个数之间的关系表达式.研究结果可以为解释离子、原子碰撞过程中产生的X射线谱提供重要的理论支持.     

20—50MeV O5+离子引起Au的L壳层X射线产生截面研究

在北京13 MV串列加速器上利用20—50MeV O⁵⁺离子研究Au的L壳层X射线产生截面. 实验结果表明σ（Ll）/σ（Lα） ,σ（Lβ）/σ（Lα） 和σ（Lγ）/σ（Lα）与EＣＰSSR理论计算结果符合比较好.在实验中由于较高的能量,在能量点存在能移现象. 关键词： 产生截面 ECPSSR X射线     

高电荷态Ar~(17+)离子在表面以下过程中发射X射线分支比及各分支能量的研究

对低速高电荷态Ar17+离子在与不同金属靶相互作用过程中放出的Ar离子K壳X射线的Kβ/Kα分支比及各分支K线平均能量进行了理论研究.在文献[28,29]的基础上,通过对实验数据的分析,得到了0.3—0.8玻尔速度之间的Ar17+离子与Be,Al,Ni,Mo,Au等金属相互作用过程中入射离子发出的X射线分支比及各分支平均能量.理论上,基于导带电子俘获模型和级联跃迁模型,建立耦合方程组,以解释实验主要结果,理论结果与实验符合较好.在此基础上讨论了低速高电荷态Ar17+离子在金属表面以下的空心原子形成及退激发过程中发射K壳X射线的物理图像.     

碳离子碰撞引起的金L壳层X射线产生截面的实验研究

实验测量了20～50 MeV的C离子和Au原子碰撞中Au产生的L壳层X射线,研究了Au的L各支壳层产生截面σ(L_l)、(L_α)、(L_β)、(L_γ)和总截面的比值σ(L_(total)与入射离子能量的关系.利用L壳层的辐射跃迁几率,Croster～Kroning跃迁率和L亚壳层的荧光产额将平面波波恩近似(PWBA)和ECSSR理论计算的电离截面转换为L层X射线产生截面,并与实验结果相比较,结果表明σ(L_l)、(L_α)、(L_γ)和总截面σ(L_(total))实验测量值随入射离子的变化趋与ECPSSR和PWBA所预测的结果一致,ECSSR理论值更接近我们的实测测量值,但是数值大于实验测量结果.     

类氦C离子诱发不同金属厚靶原子的K-X射线

利用中国原子能科学研究院HI-13MV串列加速器上提供的动能为15—55 MeV的类氦C离子分别轰击Fe, Ni, Nb和Mo金属厚靶,采用HpGe探测器测量了K-X射线,获得了相应的K-X射线的发射截面.本文中由于各个靶原子外壳层电离度的不同,类氦C离子与Fe, Ni靶原子相互作用发射的K_β与K_α X射线的分支强度比随入射离子动能增加而减小,而Nb, Mo靶原子发射的K-X射线分支强度比变化不明显.利用厚靶截面公式计算了靶原子K-X射线的发射截面,并与不同的理论模型及质子的结果进行了对比.结果表明随类氦C离子动能的增大, Fe, Ni靶原子发射的K_β与K_α X射线的总产生截面与考虑多电离的两体碰撞近似修正模型最为符合Nb, Mo靶原子发射的K_β与K_α X射线的总产生截面与平面波恩近似模型的理论值最为接近.质子与单核子C离子能量相同时,质子比类氦C离子激发不同靶的K-X射线产生截面约小3个数量级.     

光子碰撞Au靶产生L系特征X射线角分布

采用中心能量为13.1 keV (最大能量小于30 keV)的轫致辐射光子碰撞Au靶,在130°—170°的探测角度范围内以10°为间隔,测量了碰撞产生的特征X射线L_ι, L_α, L_β和L_(γ1)的光谱.根据实验测得的能谱结果,综合考虑探测器的探测效率及靶材的吸收校准后,计算了不同探测角度下特征X射线L_α与LL_(γ1)及L_ι与L_(γ1)的相对强度比;而且,还基于不同探测角度下X射线强度比值,分析了特征X射线的角分布情况.实验结果表明特征X射线L_α和L_ι为各向异性发射.此外,计算了特征X射线Li的各向异性参数为0.25,并据此推断出L_3支壳层的定向度A_(20)为0.577±0.081;分析认为L_3支壳层的定向度A_(20)由该支壳层本身的物理特性决定,但该支壳层的各向异性参数b会受到Coster-Kronig跃迁的影响而发生改变.     

高能脉冲C~(6+)离子束激发Ni靶的K壳层X射线

精确测量离子与原子碰撞引起的靶原子内壳层电离截面,对研究原子内壳层过程以及建立合适的理论模型具有重要的意义.现有的实验数据和理论模型大都集中在中低能区,高能区由于受到实验条件的限制,几乎没有相关实验数据的报道,哪种理论更适合描述高能重离子入射的靶原子内壳层电离截面,还需要进行深入的实验研究.采用电子冷却存储环提供能量分别为165,300,350,430 MeV/u的C~(6+)离子束轰击Ni靶,测量Ni的K壳层X射线.分析了实验中探测到的Ni的K_β和K_α射线强度比,发现入射粒子能量的变化对该强度比影响不明显.分别应用两体碰撞近似(BEA)、平面波玻恩近似(PWBA)和ECPSSR理论对Ni的K壳层X射线的产生截面进行理论计算,并将理论结果与实验结果进行比较.     

X-ray emission for Ar11+ ions impacting on various targets in the collisions near the Bohr velocity

X-ray emission from the collisions of 3 MeV Ar¹¹⁺ ions with V, Fe, Co, Ni, Cu, and Zn is investigated. Both the x-rays of the target atom and projectile are observed simultaneously. The x-ray yield is extracted from the original count. The inner-shell ionization cross section is estimated by the binary encounter approximation model and compared with the experimental result. The remarkable result is that the Ar K-shell x-ray yield is diminished with the target atomic number increasing, which is completely opposite to the theoretical calculation. That is interpreted by the competitive consumption of the energy loss for the ionization of inner-shell electrons between the projectile and target atom.     

Transfer ionization in isocharge sequence ion and Ne collisions

The dependence of the ratio R1 for transfer ionization to single capture for Cq+, Nq+, Oq+, Neq+ ions on Ne target upon the electronic structure of the projectile is studied. For Aq+-Ne collisions the ratio R1 decreases as the atomic number Z of the projectile increases for q=4,5,6,7 sequences which provides strong evidence for the increase of the binding energy of the target valence electron after single electron capture. The increase in binding energy depends both upon the atomic number of the projectile and the target atom.     

裸核离子与中性原子碰撞电离过程的理论研究

基于处理裸核离子与中性原子碰撞电离过程的OBKN和ECPSSR理论模型,系统计算了不同裸核离子与中性原子碰撞K壳层电子俘获截面和直接电离截面,并与其它文献已有的理论和实验结果进行了比较.研究结果表明:碰撞能量较低时,电子俘获截面大于直接电离截面,随着碰撞能量的增加,电子俘获截面和直接电离截面均是先增大后减小且直接电离截面减小地非常缓慢,高能时,直接电离截面大于电子俘获截面.当入射炮弹离子速度接近0.67倍靶原子K壳层电子速度时,电子俘获截面达到最大值,而当入射炮弹离子速度接近靶原子K壳层电子速度时,直接电离截面达到最大值.     

裸核离子与中性原子碰撞电离过程的理论研究

基于处理裸核离子与中性原子碰撞电离过程的OBKN和ECPSSR理论模型,系统计算了不同裸核离子与中性原子碰撞K壳层电子俘获截面和直接电离截面,并与其它文献已有的理论和实验结果进行了比较.研究结果表明：碰撞能量较低时,电子俘获截面大于直接电离截面,随着碰撞能量的增加,电子俘获截面和直接电离截面均是先增大后减小且直接电离截面减小地非常缓慢,高能时,直接电离截面大于电子俘获截面.当入射炮弹离子速度接近0.67倍靶原子K壳层电子速度时,电子俘获截面达到最大值,而当入射炮弹离子速度接近靶原子K壳层电子速度时,直接电离截面达到最大值.     

Measurements of L subshell and L shell x‐ray fluorescence cross‐sections for U and Th

The Ll, Lα_{1, 2}, Lη, Lβ₆, Lβ_{2, 4, 15, 17}, Lβ_{1, 3, 5}, Lβ_{9, 10}, Lγ₁, Lγ_{2, 3, 6, 8}, Lγ_4,4′ and Lγ₅ x‐ray fluorescence cross‐sections for U and Th were measured at 59.5 keV incident photon energy by using theoretical L_i subshell photoelectric cross‐sections, fluorescence and Coster–Kronig yields and fractional emission rates, and calculated theoretically by using atomic parameters. The measured values were compared with the theoretical values and experimental results available in the literature. Copyright © 2003 John Wiley & Sons, Ltd.     

Inner-shell ionization of atoms by electron,positron and photon impacts

Plane wave Born approximation with Coulomb, relativistic and exchange corrections is employed to obtain L1-, L2- and L3-subshell ionization cross sections of several atoms due to electron and positron impacts for projectile energy varying from the threshold of ionization to 60 times the threshold energy. Photoionization cross sections for all the three L-subshells of the atoms are also calculated using the hydrogenic approximation for the atomic wave functions. For L3-subshell the present cross sections due to electron impact are in good agreement with a number of experimental data for different atoms over the entire energy range investigated. For L1- and L2-subshells the present calculations yield qualitative agreement with the experimental data. The agreement between the present results and the limited experimental data for positron impact is also satisfactory. The hydrogenic approximation for the L-subshell photoionization is found to be good at small photon energies but it underestimates the cross sections at large photon energies.     

K-shell X-ray production for fluorine ions on target elements Ti to La

The production of target atomK-shell X-rays has been studied for 2 to 28 MeV fluorine ions incident on thin solid targets of 14 elements with atomic numbers Z₂=22 to 57. Total X-ray production cross sections, energy shifts ofK _α andK _β lines andK _α/K _β intensity ratios were measured with a Si(Li) detector. The results of cross section measurements are compared with theoretical predictions of inner shell ionization. In most cases, satisfactory agreement between measured cross sections and theoretical Coulomb ionization cross sections, corrected for the perturbation of the target atom by the projectile charge and for relativistic effects, was obtained.     

Cross sections of electron capture and electron capture ionization versus the impact parameter in collisions of a proton with multielectron atoms

The absolute differential cross sections of scattering of hydrogen atoms resulting from an electron capture and an electron capture ionization are measured for collisions of 4.5- and 11-keV protons with argon and xenon atoms. The range of scattering angles is 0°–2°. From the scattering differential cross section found experimentally, the probabilities of single-electron capture and electron capture ionization as a function of the impact parameter are calculated. The dependences of the incident particle scattering angle on the impact parameter (deviation function) for interactions with Ar and Xe atoms are calculated in terms of classical mechanics using the Moliére—Yukawa potential to describe the interaction of atomic particles. Analysis is given to the probabilities of electron capture and electron capture ionization versus the impact parameter and to the distribution of the electron density on different electron shells in a target atom versus a distance to the core. It is concluded that only electrons from the outer shell of the target atom are involved in the process of electron capture ionization. The cross section of electron capture ionization is calculated in the proton energy range 5–20 keV.     

Deep-core dielectronic-capture resonances in the electron-impact ionization of heavy atomic ions

Experimental measurements and theoretical calculations are carried out for the electron-impact ionization of Sm(12+). The low energy region of the single ionization cross section for Sm(12+) is found to be dominated by contributions from the indirect process of excitation autoionization. At about 1.0 keV strong resonance features are found in the experimental crossed-beam measurements performed in scan mode at high resolution. Theoretical calculations confirm that the high energy experimental features are due to deep-core dielectronic capture followed by sequential double Auger decay. The discovery of these unusual high energy resonances in single and multiple ionization opens the door for future systematic studies of how heavy atomic ions with deep inner-shell vacancies achieve final stabilization.