Anion emission from water molecules colliding with positive ions: Identification of binary and many-body processes

Chesnel, J. -Y. and Juhász, Zoltán and Lattouf, E. and Tanis, J. A. and Huber, B. A. and Bene, Erika and Kovács, Sándor and Herczku, Péter and Sulik, Béla (2015) Anion emission from water molecules colliding with positive ions: Identification of binary and many-body processes. PHYSICAL REVIEW A, 91 (6). ISSN 2469-9926

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Abstract

It is shown that negative ions are ejected from gas-phase water molecules when bombarded with positive ions at keV energies typical of solar-wind velocities. This finding is relevant for studies of planetary and cometary atmospheres, as well as for radiolysis and radiobiology. Emission of both H- and heavier (O- and OH-) anions, with a larger yield for H-, was observed in 6.6-keV 16O+ + H2O collisions. The ex- perimental setup allowed separate identification of anions formed in collisions with many-body dynamics from those created in hard, binary collisions. Most of the ani- ons are emitted with low kinetic energy due to many-body processes. Model calcu- lations show that both nucleus-nucleus interactions and electronic excitations con- tribute to the observed large anion emission yield.

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