Laser-Assisted Electron and Positronium Collisions

Low-energy electrons and their antiparticles, positrons, play a critical role in many environments and many fundamental processes. Collisions involving these particles are important in many applied fields including technological plasmas, astrophysics, atmospheric physics, and radiation damage. Collisions involving positronium, the simplest matter-antimatter atom consisting of electron and positron, are under intense studies in several experimental groups around the world. Answers to the big question why matter dominates over antimatter in our universe require studies involving the simplest antimatter atom, antihydrogen. Creation of antihydrogen atoms can be accomplished by colliding antiprotons with positronium atoms. These processes are currently investigated at the Large Hadron Collider, which provides the powerful source of antiprotons. The present project will include theoretical studies of collisions involving electrons, positrons and positronium atoms and their control by laser fields. It will have impact in studies of fundamental properties of antimatter. The proposal involves interdisciplinary efforts and international collaborations. Supervision of graduate students will promote their training in diverse areas of physics. A variety of classical, semiclassical and quantum methods will be employed to study theoretically electron and positronium (Ps) collisions with atoms, molecules, protons and antiprotons. These studies will be supplemented by investigation of laser-assisted electron and Ps collisions, particularly laser-assisted radiative recombination, dissociative recombination, Ps formation, and charge transfer in Ps collisions with protons and antiprotons. In the area of electron and Ps collisions with protons the project will focus on development of classical and semiclassical methods which were justified in previous calculations. Ps-molecule collisions will be treated quantum-mechanically with the use of free-electron-gas model with orthogonality constraints for description of exchange and correlations. 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.