Low-Energy Atomic Processes Including Ones Involving A Positron

少体系统在原子物理学和核物理学中具有重要意义。理论原子物理学中提出的研究涉及带电粒子的少体系统，特别是涉及电子的反粒子，即正电子的系统。其中一个系统是正电子负离子，它由两个电子和一个正电子组成。这种奇异的正电子原子与传统的氢原子类似，但是原子中的正电荷是正电子而不是质子。对这些少体带电系统的拟议研究将支持与英国和日本科学家的国际合作。PI是北德克萨斯大学的物理学女正教授，这是一所一流的研究型大学，也是一所西班牙裔服务机构。她计划利用这个项目包括一些能让这些学生受益的活动，并将继续指导两名研究生攻读博士学位。学生将接受分析和数值技术方面的培训，并鼓励他们在专业会议上展示他们的成果。提出了两个主要项目。第一个项目是计算电子-正电子散射的散射特性（相移和横截面），并确定正电子负离子的光剥离横截面。最近已观察到正电子负离子的光分离。第二个项目是确定氦原子的相移和正电子和电子散射的横截面，使用将氦原子视为单电子原子的模型势。先前用于正电子-氦散射的模型势的形式简化了低能弹性电子-氦散射的电子交换处理。最近的实验表明，在一定的速度范围内，正电子散射的总积分截面与电子散射的总积分截面是相似的，它是弹丸入射速度的函数。然而，在较低的速度下，正电子散射的总积分截面通常与正电子和电子散射不同。计划在散射计算中使用Kohn和逆Kohn变分方法。这些方法是非微扰的，适合在相关性很重要的低能量下使用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Few-body systems are important in atomic physics and nuclear physics. The proposed research in theoretical atomic physics involves few-body systems of charged particles, especially ones that involve the antiparticle of the electron, which is a positron. One of these systems is the positronium negative ion, which is comprised of two electrons and a positron. The exotic positronium atom is similar to the conventional hydrogen atom, but the positive charge in the atom is a positron rather than a proton. The proposed studies of these few-body charged systems will support international collaborations with scientists in the UK and Japan. The PI is a female full professor of physics at the University of North Texas, which is a Tier One Research University and a Hispanic Serving Institution. She plans to use the project to include activities that can benefit these students and will continue mentoring two graduate students toward their Ph.D. degree. Students will be trained in analytical and numerical techniques and be encouraged to present their results at professional conferences. Two main projects are proposed. The first project is the computation of scattering properties (phase shifts and cross sections) for electron-positronium scattering and the determination of the photodetachment cross section of the positronium negative ion. The photodetachment of the positronium negative ion has been recently observed. The second project is the determination of phase shifts and cross sections for both positron and electron scattering from a helium atom, using a model potential that treats helium as a one-electron atom. The form of the model potential, which has been previously used for positron-helium scattering, simplifies the treatment of electron exchange for low-energy elastic electron-helium scattering. Recent experiments have shown that the total integrated cross section for positronium scattering for a number of targets, as a function of the projectile incoming velocity, is similar to that for electron scattering for a range of velocities. However, at the lower velocities, the total integrated cross section for positron scattering is in general different from both positronium and electron scattering. It is planned to use the Kohn and inverse Kohn variational methods in the scattering calculations. These methods are non-perturbative and are appropriate to use at low energies where correlations are important.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.