Scattering of atoms and molecules off a barium zirconate surface 

S. Jans, P. Wurz, R. Schletti, K. Brining, K. Sekar, W. Heiland, J. Quinn, 
and R.E. Leuchtner


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+, 00, O+ and O at 500 3000 eV
primary energy per atom off a BaZrO3 surface. When scattering H+, H+ and Ho at
300-1500 eV per atom off the BaZrO3 surface, 35% 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. © 2001 Elsevier Science B.V. All rights reserved.

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Nuclear instruments and Methods in Physics Research B, 173(4), 503-515, 2001