The use of ion‐atom collisions to study the autoionizing states of atoms was discovered by Rudd while a professor at Concordia College in Moorhead, MN. The technique has been used to study the autoionizing transitions in target atoms and projectile ions, and to study the collisions that form the excited states. The doubly excited states of helium are still being investigated in collision experiments within the framework of the few‐body problem. ©1996 American Institute of Physics.