Collision physics involving cluster ion projectiles

An overview is given of the recent development in atomic collision physics using high-energy cluster-ion projectiles. Contrary to single-ion projectiles, extremely high density of energy deposition may be attained in cluster-solid interactions. Thus, cluster effects often called as nonlinear or correlation effects are expected and have actually been observed in various experiments relevant to electronic excitation phenomena such as energy loss and secondary particle emissions of light, electrons and neutral/ionized ions. In the present article some essential and distinctive features of cluster-ion collisions are reviewed along with introducing recent experimental results revealing typical correlation effects. (author)