Angular correlation studies of heavy-particle impact excitation of atoms

A review is given of recent developments of angular correlation studies of heavy-particle impact excitation of atoms and molecules. After a brief discussion of the basic principles of experimental methods a theory of measurement of angular correlations from heavy-particle atom collisions is outlined in the following way. By applying angular correlation measurements a subensemble from the collision processes is selected which is described by state and scattering parameters. These parameters (scattering amplitudes and their phases, alignment and orientation, state multipoles and coherence parameters) can be connected with the experimental angular correlation data. Results from heavy-particle angular correlations have been discussed in separate sections with ions or atoms as projectiles; subsections are dealing with charge exchange excitation, excitation of autoionizing states, direct and simultaneous excitation of target and projectile particles. The angular correlation parameters are very sensitive to the detailed excitation mechanisms and quasi-molecular parameters in heavy-particle atom collisions. The majority of data available so far were obtained from simple projectile-target systems such as one-electron atom systems and are rare gas atoms. Attention is drawn to possible spin-orbit effects in the analysis of angular correlations from collisions between very heavy atomic particles.