In this project, part of the Cross-Directorate program for Multidisciplinary Research in Optical Science and Engineering, William Stwalley and colleagues at the University of Connecticut will extend optical and other physical techniques for control and manipulation of atoms and atomic ions, such as cooling and trapping, to molecules and molecular ions for studies of ultracold chemical reactions and inelastic collisions. Such ultracold collision dynamics, at temperatures near 0.001 K, are virtually unexplored, but they are predicted to show extreme quantum behavior which is highly sensitive to details of the interactions, including the collision energy and quantum states involved. Ultracold molecules will be formed by photoassociation of ultracold atoms. Chemical reactions, such as between a cryogenic beam of molecular hydrogen and laser-cooled cesium atoms, will be explored in both the cold and ultracold regimes, that is, at temperatures less than 10 K and 1 mK, respectively. The techniques of laser manipulation, which have proven so fruitful with atoms, will be extended to allow investigations involving molecules and molecular ions. Novel chemical processes and physical behavior are expected to be found in the ultracold temperature region examined in this program. This interdisciplinary research will have significant educational impact at several levels.