Scattering of atoms and molecules off a barium zirconate surface

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 for 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 barium zirconate surface, Experiments were performed at two different setups, one of them including a time-of-flight (TOF) measurement of the specularly reflected particles, the other one allows position-resolved detection. We measured high fractions (22-35%) of negative ions and no positive ions when scattering O-, O-0, O-2(+) and O-2(0) at 500-3000 eV primary energy per atom off a BaZrO3, surface. When scattering H-, H-2(+) and H-2(0) at 300-1500 eV per atom off the BaZrO3 surface, 3-5% of the particles were converted into negative ions and 2-8% into positive ions. Our results suggest a complete memory loss of the incident charge state. Scattered molecules dissociated almost completely. The mean energy loss was proportional to the incident particle energy. BaZrO3 therefore meets the most important requirements for application on a space platform. (C) 2001 Elsevier Science B.V. All rights reserved.