Research
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           My research interests are in the area of experimental atomic physics where we investigate the scattering of low energy positrons (and electrons) by atoms and molecules.

 

 

Research Overview
 
          Positrons are the antiparticles of electrons, having the same mass as an electron and the opposite electric charge (plus instead of minus). The ultimate fate of a positron on Earth is annihilation with an electron where all of the mass of the positron and electron is converted into two (or more) gamma rays. The positrons used in our laboratory originate from radioactive sources of sodium-22, which decay with a 2.6 year half-life by emitting positrons. Using moderators, electric and magnetic fields, we are able to produce variable energy beams of positrons with kinetic energies ranging from about one to a few hundred electron volts (eV) suitable for doing our scattering experiments. It is only when positrons lose virtually all of their excess kinetic energy (well below one eV) that annihilation occurs.

          Our research group presently has three experimental systems for measuring cross sections (i.e., the probability) for total scattering, differential elastic scattering, and positronium formation for positrons colliding with various atoms (e.g., inert gases, hydrogen, alkali metals, magnesium) and molecules. Total scattering refers to the likelihood that a positron will be scattered in any manner (i.e., elastic scattering, exciting or ionizing the target atoms or molecules, and positronium formation) during a collision. Differential elastic scattering involves the study of the scattering of a projectile particle (e.g., positrons) at different angles with respect to its initial direction of motion for collisions where kinetic energy is conserved. Positronium is formed when a positron combines with an electron to produce a very short-lived atom, that decays by emitting two or more gamma rays.

          Investigations of positron interactions with atoms and molecules provide information about the interaction of antimatter with regular matter that is potentially useful in a variety of applications in science and technology. For example, information from such studies is helping astrophysicists to interpret what is happening in solar flares and the direction towards the center of our Milky Way Galaxy (where a supermassive black hole most likely exists), from which characteristic positron annihilation gamma rays have been observed. In addition, comparisons between positron and electron scattering by atoms and molecules help to provide a better understanding of fundamental scattering processes in atomic physics.

Publications

Chapters Published and Editorship of Book
Journal Articles Published
Invited Review Articles
Papers Published in Conference Proceedings

 

 
This research is supported by the National Science Foundation.
Send mail to kauppila@physics.wayne.edu  
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Copyright 2010 Department of Physics & Astronomy, Wayne State University
Last modified on: May 26, 2010