Thermal-energy scattering of atoms in high Rydberg states. Annual progress report, July 1, 1978--June 30, 1979. [Summaries of research activities at Oregon State Univ

Abstract

This research consists of an experimental study of the scattering of free atoms in high Rydberg states and their interaction with ground-state atomic and molecular targets. The highly excited Rydberg states, lying just below the ionization limit, describe a single weakly bound electron moving around a positive ion core. These states are characterized by large principal quantum numbers, long radiative lifetimes, and large cross sections for certain scattering processes. In the proposed investigations, differential cross sections will be measured for the deflection of high Rydberg atoms from an atomic beam. Preliminary scattering experiments, completed in the laboratory, have yielded cross sections which are virtually independent of the principal quantum number and in good agreement with calculations for deflection of the core ion alone. The deflection was also observed directly. If the momentum transfer takes place as an essentially free-ion process, then it is possible to obtain ion-scattering cross section from measurements with Rydberg atoms as projectiles. The presence of a distant valence electron provides a charge-neutralizing sheath surrounding the ion core, rendering its trajectory virtually unaffected by non-ionizing external fields. Since ion-beam scattering experiments have heretofore proven difficult at thermal energies, this research program seeks to develop and exploit a useful new method for the determination of velocity-resolved free-ion differential cross sections and the functional form of ion-atom and ion-molecule interaction potentials.