(e,gamma,2e) Threshold Spectroscopy - A new method to study collisional excitation of atoms using combined laser and electron beams

(e,gamma,2e) 阈值光谱 - 一种使用激光和电子束组合来研究原子碰撞激发的新方法

• 批准号: EP/W003864/1
• 负责人: Andrew Murray
• 金额: $ 64.38万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FW003864%2F1
• 关键词: gamma; 2e; Threshold; Spectroscopy; new

Since the foundation of modern physics where Rutherford and collaborators discovered the structure of the atom in Manchester and Neils Bohr developed the first quantum theory, collision experiments between an incident particle and an atomic target have provided physicists with precise details on the nature of matter. Rutherford's experiments probed the nucleus and its size using alpha particles, leading to modern nuclear physics. The work of Franck and Hertz soon after used electron beams to probe the structure of the electrons surrounding the nucleus. This work lead to the development of modern quantum theory and atomic physics. Since that time our understanding of the atom and its structure (which has been learned through developing theories and more sophisticated experiments) has paved the way to the development of almost all technologies that we use today. Key to these successes and to the future development of new and emerging technologies is the close collaboration between experimentalists who measure the interactions to high precision and theoreticians who develop the quantum theories that describe these processes. By testing theory with experiment the models are refined and improved, allowing them to accurately predict what happens in many areas of modern science and industry. Processes where the models have direct application include the development of new lasers, in Tokomaks for the generation of fusion energy, in the earth's upper atmosphere (including the ozone layer and ionosphere) and in areas of astrophysical interest including for models of stellar atmospheres and in the atmosphere of exoplanets. Understanding excitation of atoms by electron impact hence plays an essential role in testing different models of the interaction. Results from experiment and theory have converged in recent years, with the models now agreeing well when compared to existing experimental data. The conventional experiments that are used are however limited due to the low efficiency of the detectors or due to limitations of the techniques that are adopted. They therefore cannot measure the excitation of a wide range of target states, including higher lying states that have long lifetimes and metastable states where the atom effectively 'stores' the energy imparted by the collision for a long time. Understanding excitation of these 'metastable' atoms hence is important in many different areas.The new technique that has been proposed here will allow these types of interactions to be studied for the first time. This will be carried out by using a very precise laser beam to further excite the atoms created by the collision to a highly excited Rydberg state that is very close to ionization. These 'Rydberg atoms' can be huge - we can make neutral atoms in our laboratory that have diameters around 1/10th that of a human hair. These enormous atoms can very easily be ionized by applying a small electric field that releases the electron from the atom, which we can then detect. By measuring the ensuing electron yield and by changing the polarization of the laser beam, we can then extract all information about the initial collision in a unique way and with high efficiency. The new experimental technique proposed here hence complements that of existing methods without suffering from the technological limitations that occur with them. The experiments will therefore provide new data to test the quantum models, allowing them to be further refined, enhanced and improved.

卢瑟福和他的合作者在曼彻斯特发现了原子的结构，尼尔斯·玻尔提出了第一个量子理论，自现代物理学建立以来，入射粒子和原子目标之间的碰撞实验为物理学家提供了关于物质本质的精确细节。卢瑟福的实验利用α粒子探测了原子核及其大小，开创了现代核物理学。不久之后，弗兰克和赫兹的工作使用电子束探测原子核周围电子的结构。这项工作导致了现代量子理论和原子物理学的发展。从那时起，我们对原子及其结构的理解（通过不断发展的理论和更复杂的实验来了解）为我们今天使用的几乎所有技术的发展铺平了道路。这些成功的关键和新兴技术的未来发展是密切合作的实验家谁测量的相互作用，以高精度和理论家谁发展量子理论，描述这些过程。通过用实验检验理论，这些模型得到了完善和改进，使它们能够准确地预测现代科学和工业许多领域发生的事情。这些模型有直接应用的过程包括开发新的激光器，在托科马克用于产生聚变能，在地球的高层大气（包括臭氧层和电离层），以及在天体物理学感兴趣的领域，包括恒星大气模型和系外行星的大气。因此，理解电子碰撞对原子的激发在测试相互作用的不同模型中起着至关重要的作用。近年来，实验和理论的结果趋于一致，模型与现有的实验数据相比较，现在符合得很好。然而，由于探测器的低效率或所采用的技术的限制，所使用的传统实验受到限制。因此，它们无法测量大范围目标态的激发，包括具有长寿命的高能级态和亚稳态，其中原子有效地“储存”了长时间碰撞所传递的能量。因此，了解这些“亚稳态”原子的激发在许多不同的领域都很重要。这里提出的新技术将允许首次研究这些类型的相互作用。这将通过使用非常精确的激光束来进一步激发由碰撞产生的原子，使其达到非常接近电离的高度激发里德伯态来实现。这些“里德伯原子”可以是巨大的——我们可以在实验室里制造出直径约为人类头发十分之一的中性原子。这些巨大的原子可以很容易地被电离，只要施加一个小电场，从原子中释放出电子，然后我们就可以探测到。通过测量随后的电子产率和改变激光束的偏振，我们可以以一种独特的方式高效地提取出关于初始碰撞的所有信息。因此，这里提出的新的实验技术是对现有方法的补充，而不会受到与之相关的技术限制。因此，这些实验将为测试量子模型提供新的数据，使它们能够进一步完善、增强和改进。

项目成果

Measurement of argon ( e , 2 e ) differential cross sections in the perpendicular plane from 5 to 200 eV above the ionization threshold

在高于电离阈值 5 至 200 eV 的垂直平面内测量氩 ( e , 2 e ) 微分截面

• DOI: 10.1103/physreva.105.042815
• 发表时间: 2022
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Patel M

Laser-atom interaction simulator derived from quantum electrodynamics

基于量子电动力学的激光-原子相互作用模拟器

• DOI: 10.1103/physreva.105.053117
• 发表时间: 2022
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Patel M

Evolution of the xenon ( e , 2 e ) differential cross section from a coplanar geometry to the perpendicular plane in the intermediate-energy regime

中能状态下氙 ( e , 2 e ) 微分截面从共面几何到垂直平面的演化

• DOI: 10.1103/physreva.105.032818
• 发表时间: 2022
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Patel M

Measurements of the Kr (e, 2e) differential cross section in the perpendicular plane, from 2 eV to 120 eV above the ionization threshold

垂直平面中 Kr (e, 2e) 微分截面的测量，电离阈值以上 2 eV 至 120 eV

• DOI: 10.48550/arxiv.2304.00956
• 发表时间: 2023
• 作者: Murray A

An undergraduate physics experiment to measure the frequency-dependent impedance of inductors using an Anderson bridge

使用安德森电桥测量电感器频率相关阻抗的本科物理实验

• DOI: 10.1119/5.0148114
• 发表时间: 2023
• 期刊: American Journal of Physics
• 影响因子: 0.9
• 作者: Murray A