Biological Warfare: A Nation at Risk - A Time to Act

Abstract
A series of hyperthermal energy, ion/surface scattering experiments were performed. These studies examined and characterized some of the many processes occurring in energetic gas/surface collisions. In the scattering of Ne+ on Si(001), the precise amount of momentum, transferred to the surface upon collision, was measured under various conditions. Models that incorporate image charge interactions and inelastic energy loss were successfully applied to simulate the data. The first measurement of atom abstraction at an oxide surface was recorded in the scattering of NO+ on O/Al(111). Measurement of the product yield and energy distribution as a function of incident energy revealed the detailed reaction mechanism. The growth and erosion of SiO2 thin films under O+ bombardment was studied. Isotopic labeling experiments combined with mass-, energy-, and angular-resolved detection provided compelling evidence for a direct Eley-Rideal abstraction of adsorbed oxygen by incident O+ ions. This reaction pathway competes directly with sputtering channels in the formation of scattered O2- and SiO+. The conclusions from this work help in the modeling of spacecraft interactions with the LEO environment, e.g., vehicle drag, spacecraft charging, oxidation/degradation of exposed surfaces, and the formation of signatures.

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