Radiative Double Electron Capture (RDEC) of Ions with Quasi-free Electrons

准自由电子对离子的辐射双电子捕获 (RDEC)

• 批准号: 1707467
• 负责人: Asghar Kayani
• 金额: $ 12万
• 依托单位: Western Michigan University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-10-01 至 2023-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1707467&HistoricalAwards=false
• 关键词: Radiative; Double; Electron; Capture; RDEC

A popular image of atoms shows electrons circling the nucleus like planets orbiting the sun. To improve upon this analogy, one must understand how electrons in atoms repel each other due to their negative charges, and how electrons obey the laws of quantum mechanics. This project studies how interactions between electrons causes their motion to become correlated. This is important because such correlations have a big impact on the physical and chemical properties of atoms, molecules, and materials. To investigate electron correlations, this project will observe situations in which two electrons are transferred from one atom to an ion and an x-ray photon is simultaneously emitted. When this happens, the entire process can be thought of as the time inverse of double ionization (removal of two electrons) by a single photon. This is related to the photoelectric effect, which was originally explained by Albert Einstein in 1905. However, the rate for double photoionization is difficult to predict because of the way electrons interact with one another. Similar physics is important when two electrons are transferred to a moving projectile. Scientists are interested in understanding this process as it occurs in collisions between projectile ions and target atoms and from the time-reversed process of double photoionization of an atom by a single photon. Both processes are likely to occur in astrophysical plasmas. Probabilities for the two-electron process have been calculated with widely differing results, leaving the field open for experiments to resolve the differences. Attempts to measure the process have been very difficult due to the long measuring times required to observe the events. The involvement of Ph.D. students in this research project gives them valuable training in a state-of-the-art physics experiment and experience in preparing collaborative manuscripts and abstracts and allows them to attend conferences to report the results and assists them as they develop into productive young scientists.The transfer of two electrons to an ion accompanied by the emission of a single photon is called radiative-double-electron capture, or RDEC for short. The intellectual merit of this proposal lies in its intrinsic importance in the field of ion collisions with quasi-free electrons, and its close relationship to photon interactions with highly-charged ions. This relationship comes about because RDEC is the time inverse of double photoionization. These processes are essentially identical when RDEC occurs for incident fully-stripped ions and double photoionization for two-electron systems, in which case the interaction between the two electrons, i.e., correlation, plays a fundamental role. RDEC is similar to the commonly observed one-electron process of radiative-electron capture (REC), the inverse of the photoelectric effect, which, however, does not require electron correlation. New studies in this project of RDEC for gas targets of helium, nitrogen and neon will address complications of previously published data involving ion-solid interactions for oxygen and fluorine ions incident on a thin C-foil target. Multiple collision effects are not present for gas targets as they are for solid targets. RDEC can be compared with several published theoretical calculations, which, however, differ by several orders of magnitude. The measurements are being done (Some preliminary data have already been obtained for nitrogen and neon targets.) for fully-stripped fluorine ions using the 6-MV tandem Van de Graaff accelerator at Western Michigan University. Coincidences between x rays emitted and singly- and doubly-charged projectiles are recorded, with the latter representing a signature for RDEC. The measurements are very time-consuming due to the relatively small RDEC cross sections (less than ~1 barn) and require continuous counting times of a month or more for each target. The studies are carried out by the PI, the co-PI, and two graduate students and also include collaborators from the University of Notre Dame and Jagiellonian University in Krakow (Poland).

一张流行的原子图像显示电子绕着原子核旋转，就像行星绕着太阳旋转一样。 为了改进这一类比，我们必须了解原子中的电子如何因其负电荷而相互排斥，以及电子如何遵守量子力学定律。 该项目研究电子之间的相互作用如何使它们的运动变得相关。这很重要，因为这种相关性对原子、分子和材料的物理和化学性质有很大影响。 为了研究电子相关性，该项目将观察两个电子从一个原子转移到一个离子并同时发射 X 射线光子的情况。 当这种情况发生时，整个过程可以被认为是单个光子双电离（去除两个电子）的时间倒数。这与光电效应有关，光电效应最初由阿尔伯特·爱因斯坦于 1905 年解释。然而，由于电子彼此相互作用的方式，双光电离的速率很难预测。 当两个电子转移到移动的射弹时，类似的物理现象很重要。科学家们有兴趣了解这个过程，因为它发生在射弹离子和目标原子之间的碰撞中，以及单个光子对原子进行双光电离的时间反转过程。这两个过程都可能发生在天体物理等离子体中。双电子过程的概率计算得出的结果差异很大，为解决这些差异的实验留下了空间。由于观察事件需要很长的测量时间，尝试测量该过程非常困难。博士的参与。该研究项目的学生为他们提供了最先进的物理实验的宝贵培训以及准备合作手稿和摘要的经验，并允许他们参加会议报告结果并帮助他们成长为富有成效的年轻科学家。两个电子转移到一个离子并伴随着单个光子发射的过程称为辐射双电子捕获，简称 RDEC。该提议的智力价值在于其在离子与准自由电子碰撞领域的内在重要性，以及其与光子与高电荷离子相互作用的密切关系。出现这种关系是因为 RDEC 是双光电离的时间倒数。当 RDEC 发生在入射完全剥离离子和双电子系统的双光电离时，这些过程本质上是相同的，在这种情况下，两个电子之间的相互作用（即相关性）起着基本作用。 RDEC 类似于常见的辐射电子捕获 (REC) 的单电子过程（光电效应的逆过程），但不需要电子关联。该 RDEC 项目针对氦、氮和氖气体靶材的新研究将解决先前发表的数据的复杂性，这些数据涉及薄 C 箔靶材上发生的氧和氟离子的离子-固体相互作用。气体目标不像固体目标那样存在多重碰撞效应。 RDEC 可以与一些已发表的理论计算进行比较，但两者相差几个数量级。正在使用西密歇根大学的 6-MV 串联范德格拉夫加速器对完全剥离的氟离子进行测量（已经获得了氮和氖目标的一些初步数据。）。记录发射的 X 射线与单电荷和双电荷射弹之间的一致性，后者代表 RDEC 的签名。由于 RDEC 横截面相对较小（小于约 1 个谷仓），测量非常耗时，并且需要对每个目标进行一个月或更长时间的连续计数。这些研究由 PI、联合 PI 和两名研究生进行，其中还包括来自圣母大学和克拉科夫雅盖隆大学（波兰）的合作者。

项目成果

Target K-shell X-ray emission associated with single and double electron capture for F9+,8+,7+ + Ar collisions

与 F9 ,8 ,7 Ar 碰撞的单电子和双电子捕获相关的目标 K 壳层 X 射线发射

• DOI: 10.1016/j.nimb.2020.04.027
• 发表时间: 2020
• 期刊: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
• 作者: La Mantia, D.S.;Kumara, P.N.S.;Tanis, J.A.
• 通讯作者: Tanis, J.A.

Radiative double-electron capture for oxygen and fluorine ions colliding with thin-foil C: Effects of multiple collisions

氧和氟离子与薄膜 C 碰撞的辐射双电子捕获：多次碰撞的影响

• DOI: 10.1103/physreva.102.060801
• 发表时间: 2020
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: La Mantia, D. S.;Kumara, P. N.;McCoy, C. P.;Tanis, J. A.
• 通讯作者: Tanis, J. A.

Observation of Radiative Double Electron Capture for Fluorine Ions on Nitrogen and Neon

氮和氖上氟离子的辐射双电子捕获观察

• DOI: 10.1088/1742-6596/875/2/012014
• 发表时间: 2017
• 期刊: Journal of Physics: Conference Series
• 作者: La Mantia, D S;Kumara, P N;Niraula, P M;Iqbal, S;Bridges, M C;Kayani, A;Simon, A;Tanis, J A
• 通讯作者: Tanis, J A

Observation of radiative double electron capture for

辐射双电子捕获的观测

• DOI: 10.1002/xrs.3063
• 发表时间: 2019
• 期刊: X-Ray Spectrometry
• 影响因子: 1.2
• 作者: Kumara, Nuwan;La Mantia, David S.;Buglione, Stephanie L.;McCoy, Craig P.;Taylor, Charles J.;White, Jacob S.;Kayani, Asghar;Tanis, John A.
• 通讯作者: Tanis, John A.

Radiative Double-Electron Capture by Bare and One-Electron Ions on Gas Targets

裸电子离子和单电子离子对气体靶材的辐射双电子捕获

• DOI: 10.1103/physrevlett.124.133401
• 发表时间: 2020
• 期刊: Physical Review Letters
• 影响因子: 8.6
• 作者: La Mantia, D. S.;Kumara, P. N. S.;Buglione, S. L.;McCoy, C. P.;Taylor, C. J.;White, J. S.;Kayani, A.;Tanis, J. A.
• 通讯作者: Tanis, J. A.