In this project in the Physical Chemistry program of the Chemistry Division, Professors F. Barry Dunning and Ken A. Smith of the Chemistry Department of William Marsh Rice University will engage in a continuing series of investigations of electron-molecule and ion-molecule reactions. In the present work the emphasis is on reactions in which atoms in high Rydberg states participate. Specific problems addressed are the lifetimes of collision intermediates and their stabilization through energy transfer via interactions with a third collision partner. In addition, Rydberg atoms will be used to study energy transfer in ion-ion collisions, and create dipole bound negative ions and investigate their properties. Rydberg atoms (or molecules) are systems in which an electron is in a sufficiently large orbit so that the whole system resembles that of an excited hydrogen atom. With increasing excitation the electron goes into increasingly larger orbits until it becomes free of the rest of the atom which thereby becomes an ion. Chemical reactions in which ions participate play a major role and a full understanding of the reaction kinetics and dynamics requires, among others, a detailed knowledge of the ion-ion, ion-molecule, and electron- molecule collision processes. The research conducted here is directed toward obtaining such knowledge.