Coherence Effects and Few-Body Dynamics in Atomic Fragmentation Processes

原子碎片过程中的相干效应和少体动力学

• 批准号: 1401586
• 负责人: Michael Schulz
• 金额: $ 50.74万
• 依托单位: Missouri University of Science and Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1401586&HistoricalAwards=false
• 关键词: Coherence; Effects; Few; Body; Dynamics

This work seeks to address the following basic questions. What are the forces acting in nature and what are their properties? How do systems consisting of several objects develop under the influence of these forces? The second question represents one of the most fundamental, unsolved problems in science. The motion of two objects can often be predicted with virtual certainty. For example, if the solar system consisted of only the sun and the earth, one could predict the position and the velocity of the earth relative to the sun for all times in the future. But if only one more object is added to the system (say the moon in the above example) no analytic solution (one that is given in terms of equations) within our mathematical framework exists. This dilemma is known as the few-body problem (FBP). It has very broad impacts in all of the natural sciences because most of modern research deals with systems containing more than 2 objects. The project outlined in this proposal experimentally studies the FBP for atomic systems. For such systems of microscopic scale the FBP is further complicated by the characteristics of quantum-mechanics, the theory that was designed to describe such tiny systems. In the long term, this work may influence not only the understanding of isolated atoms, but also the interaction of beams of atoms (or ions or molecules) with surfaces, something which is a key technology underpinning the manufacturing of portable electronic devices and computers.In this project the few-body problem will be studied by performing kinematically complete experiments on ionization of simple targets by ion impact. The momentum vectors of the scattered projectiles and of the recoiling target ions are measured directly and the momentum of the ejected electron is deduced from the kinematic conservation laws. From the data, fully differential cross sections (FDCS) will be extracted. The coherence properties of the projectile can be varied by changing the geometry of a collimating slit placed before the target. Only relatively recently it was discovered that the FDCS can be sensitive to the projectile coherence length. This, in turn, can explain very puzzling discrepancies between theory and experiment, which were vividly debated for the last decade. The proposed work aims at systematically exploring the role of the projectile coherence properties in atomic few-body systems. It is anticipated that the results from these studies will represent an important step forward towards a thorough understanding of the few-body problem.

这项工作旨在解决以下基本问题。自然界中作用的力是什么？它们的性质是什么？在这些力的影响下，由几个物体组成的系统是如何发展的？第二个问题代表了科学中最基本的、未解决的问题之一。两个物体的运动通常可以几乎确定地预测。例如，如果太阳系只由太阳和地球组成，人们可以预测未来所有时间地球相对于太阳的位置和速度。但是，如果只在系统中增加一个物体（比如上面例子中的月亮），在我们的数学框架内就不存在解析解（用方程给出的解）。这个问题被称为少体问题（few body problem，FBP）。它在所有的自然科学中有非常广泛的影响，因为大多数现代研究涉及包含两个以上对象的系统。本提案中概述的项目实验研究了原子系统的FBP。对于这种微观尺度的系统，FBP由于量子力学的特性而进一步复杂化，量子力学是设计来描述这种微小系统的理论。 从长远来看，这一工作不仅会影响对孤立原子的理解，还会影响原子（或离子或分子）束与表面的相互作用，这是制造便携式电子设备和计算机的关键技术。在本项目中，将通过离子碰撞电离简单目标的运动学完整实验来研究少体问题。直接测量散射粒子和反冲靶离子的动量矢量，并从运动学守恒定律推导出射出电子的动量。从数据中，将提取全微分截面（FDCS）。通过改变靶前准直狭缝的几何形状，可以改变射弹的相干特性。直到最近才发现FDCS可以对射弹相干长度敏感。这反过来又可以解释理论和实验之间令人困惑的差异，这在过去十年中引起了激烈的争论。 本文的工作旨在系统地研究原子少体系统中射弹相干性的作用。预计这些研究的结果将是朝着彻底了解少体问题迈出的重要一步。

项目成果

Fully Differential Study of Capture with Vibrational Dissociation in p + H2 Collisions

p H2 碰撞中振动解离捕获的全微分研究

• 发表时间: 2017
• 期刊: Physical review letters
• 影响因子: 8.6
• 作者: B.R. Lamichhane, T. Arthanayaka

Comparison of experimental and theoretical fully differential cross sections for single ionization of the 2 s and 2 p states of Li by Li2+ ions

Li2 离子单电离 Li 2 s 和 2 p 态的实验和理论全微分截面比较

• DOI: 10.1088/1361-6455/aa8dd2
• 发表时间: 2016
• 期刊: Journal of Physics B: Atomic, Molecular and Optical Physics
• 作者: E. Ghanbari;D. Fischer;N. Ferreira;J. Goullon;R. Hubele;A. LaForge;M. Schulz;D. Madison
• 通讯作者: D. Madison