This grant is in the general field of analytical and surface chemistry and in the subfield of dynamics of chemical reactions at surfaces. Professor Dennis Jacobs of the University of Notre Dame will study the interaction of low energy dioxygen and nitrogen oxide ions with clean single crystal surfaces of silver, silicon and gallium arsenide. The roles of the ion initial energy and geometry of the scattering on the reaction of the ion with the surface will be determined. This work will be important in understanding the processing of semiconductor materials for devices. Vibrational and rotational state resolution of the primary ion will be accomplished with resonance enhanced multiphoton ionization methods. This will allow production of hyperthermal ions for scattering and reaction across the surfaces of the silver, silicon and gallium arsenide. Microscopic dynamics of these reactions will be determined as a function of the ion initial conditions.