Collisions involving photons, electrons, ions, atoms, molecules, clusters, surfaces and exotic particles occupy the fundamental importance for the understanding of the formation of matter in the universe and knowing almost everything about the structure of matter. Large extend of the scientific endeavor lies in understanding the various natural phenomena around us. Study of Atomic - Molecular physics has been growing speedily in the light of various matter - matter, radiation - matter phenomena, which are studied upon atoms, molecules, radicals, clusters, and a few exotic targets such as dimers, metastable atoms and molecules.