Low-Energy Atomic Processes Including Ones Involving A Positron

University Of North Texas, Denton TX

Investigators

Abstract

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.