Positron-atom and positron-molecule collisions

The scattering of positrons by atoms and molecules is reviewed. The recent development of monoenergetic slow positron beams and their applications to the measurement of cross sections for positrons interacting in various gases are discussed briefly. The theoretical development of positron collisions in gases is covered from the beginning. Both elastic and the inelastic processes have been included. Comparisons are made between the measured values and theoretical predictions. The deficiencies of the theoretical models and experimental apparatus are also pointed out.