Scattering of atoms and molecules off a magnesium oxide surface

Autor(en): Wieser, M
Wurz, P
Bruning, K
Heiland, W
Stichwörter: BEAM; COLLISIONS; DEPENDENCE; HYDROGEN; Instruments & Instrumentation; IONIZATION; MASS SPECTROGRAPH; MgO; NEGATIVE-ION PRODUCTION; neutral particle imaging; Nuclear Science & Technology; particle scattering; Physics; Physics, Atomic, Molecular & Chemical; Physics, Nuclear; surface ionization
Erscheinungsdatum: 2002
Herausgeber: ELSEVIER SCIENCE BV
Journal: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS
Volumen: 192
Ausgabe: 4
Startseite: 370
Seitenende: 380
Zusammenfassung: 
Neutral particle imaging in the low energy range will, when employed in future spacecraft missions, potentially contribute to enlarging our knowledge about the origin and evolution of our universe. The main difficulty of a neutral particle detector in this energy range is that the incoming neutrals must first be ionized such that they can be mass- and energy-analyzed by conventional methods. In this paper we report on the first observation of the formation of negatively charged ions upon reflection from a magnesium oxide surface. Experiments were performed at two different setups, one of them including a time-of-flight measurement of the specularly reflected particles, the other one allows angle resolved detection. We measured high fractions (12-30%) of negative ions and less than 1% of positive ions when scattering O+, O-0, O-2(+) and O-2(0) at 90-3000 eV primary energy per atom off a MgO surface. When scattering H+, H-2(+) and H-2(0) at 300-1500 eV per atom off the MgO surface, 3-7% of the particles were converted into negative ions and 2-10% into positive ions and when scattering C+ and C-0 at 1500-2000 eV per atom around 3% of the particles were converted into negative ions and 3% into positive ions. Our results strongly suggest a complete memory loss of the incident charge state. Scattered molecules dissociated always completely. The mean energy loss was approximately proportional to the incident particle energy except for O- ions where an increased loss at lower energy was observed. MgO therefore meets the most important requirements for application on a space platform. (C) 2002 Published by Elsevier Science B.V.
ISSN: 0168583X
DOI: 10.1016/S0168-583X(02)00486-X

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