Low-Energy Atomic Processes Including Ones Involving A Positron

少体系统是原子物理和核物理中的重要组成部分。在理论原子物理学中，拟议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（正电子）的系统。其中一个系统是正电子素负离子，它由两个电子和一个正电子组成。奇异的正电子素原子与传统的氢原子相似，但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是北德克萨斯大学物理学的一名女性全职教授，该大学是一所一流的研究型大学和西班牙裔服务机构。她计划利用这个项目，包括可以使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。℃下学生将接受分析和数值技术的培训，并被鼓励在专业会议上展示他们的结果。提出了两个主要项目。第一个项目是计算电子-正电子素散射的散射性质（相移和散射截面），并确定正电子素负离子的光剥离截面。正电子素负离子的光剥离是最近才发现的。第二个项目是确定的相移和截面的正电子和电子从氦原子散射，使用模型势，把氦作为一个单电子原子。模型势的形式，这是以前用于正电子-氦散射，简化了低能量弹性电子-氦散射的电子交换的处理。最近的实验表明，总积分截面为正电子素散射的目标数，作为一个函数的弹丸入射速度，是类似的电子散射的速度范围。然而，在较低的速度下，正电子散射的总积分截面一般不同于正电子素和电子散射。计划在散射计算中使用Kohn变分法和逆Kohn变分法。这些方法是非微扰的，适用于低能量，其中相关性是重要的。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.