This program focuses on the investigation of low-energy atomic interaction phenomena and their role in coherent matter wave optics. Emphasis is placed on ground-state resonance and threshold phenomena, ultracold atom-dimer interactions, and interactions involving multiple atomic species. A new method to irreversibly produce translationally ultracold, trapped rubidium dimers in very high bound states will also be explored, and the connection between Bose condensates and atomic optics will be studied.