Negative ion collisions. Progress report, April 1, 1994--March 31, 1997

Abstract

During the last three years, the experimental activities have concentrated on several somewhat distinct projects. First, the author has measured total cross sections for electron detachment and charge transfer for collisions of various negative ions with atomic hydrogen and the molecular target, O{sub 3} (ozone). The second type of gas phase experiments investigated the collisional decomposition of the molecular ion H{sub 3}{sup +}. Specifically he has measured total cross sections for dissociation and proton transfer with an apparatus utilizing a static gas target cell. The targets include hydrogen, deuterium and the rare gases. He has extended these experiments to include D{sub 3}{sup +} in a crossed beam configuration in order to provide a more detailed understanding of the collisional dynamics for these reactants. In the area of ion-surface collisions he has measured sputtering yields for O{sup {minus}} and electrons arising from collisions of ions with an Al/O surface. The amount of oxygen on the surface is carefully controlled and the kinetic energy distributions of the ejected anions and electrons have been determined. He has been able to develop a theoretical model which, to a large degree, can describe the process. In a slightly speculative endeavor, he has begun investigating themore » role of atom-catalyzed field emission, i.e., the extent to which an unoccupied negative ion state for an atom near a surface--under the influence of a strong electric field--can serve as a stepping-stone for electron field emission. Very brief accounts of these activities will be given in this report in section 2. Detailed discussions of the experimental results and their analyses published during the contract period may be found in the following articles which have appeared in the archival literature. Copies of these publications are appended to this report as section 4.« less