This award will support collaborative research in physics between Dr. John Weiner, University of Maryland, and Dr. Francoise Masnou-Seeuws, Laboratory for Atomic and Molecular Collisions, Orsay, France. The investigators propose a cooperative program in which experiments (on the US side) and theory (on the French side) will combine to advance understand- ing of the dynamics of ultracold collisions in elementary processes. Dr. Weiner and his research group are currently carrying out experiments on associative ionization collisions in alkali atomic beams. They have performed measurements of reaction probability as a function of collision velocity, excited- state alignment and orientation, and optical-field intensity over collision temperatures, ranging from several hundred degrees Kdown to less than 1 mK. These results must be interpreted in terms of the very long-range behavior of potential curves at internuclear separations from several hundred to more than a thousand atomic units. Furthermore, close coupling theories of inelastic collisions are indispen- sible to a proper description of the scattering event. Dr. Masnous-Seeuws, a recognized world authority in these areas, and her theory group at Orsay, will apply their expertise to a thoroughgoing interprestation of the experimental results. The combined effort will lead to a clear understanding of chemical bond-forming mechanisms at ultracold temperatures.
