SYMMETRIES IN ATOMIC-COLLISIONS

General kinematic analyses of various atomic collision processes by us ing the density-matrix and helicity formulations are reviewed. The rot ation, parity, and time-reversal symmetries of the colliding systems a re considered, In addition to polarization and angular correlations in each collision process, correspondences among different collision pro cesses are also studied. As an example, the time-reversal symmetry bet ween photoionization and electron-capture fluorescence are demonstrate d explicitly, and there is a one-to-one correspondence between angular correlation functions for the two processes. The symmetry study in at omic collisions provides a great deal of valuable information about, t he colliding systems and enhances our knowledge on the collision dynam ics.