Eur. Phys. J. D 35, 267-278 (2005)
https://doi.org/10.1140/epjd/e2005-00225-3

Positrons — an alternative probe to electron scattering

Faculty of Engineering, Trento University, 38050 Povo, Italy

Corresponding author: ^a karwasz@chemie.fu-berlin.de

Received: 7 April 2004
Revised: 27 May 2005
Published online: 17 August 2005

Abstract

Interaction of positrons with atoms and molecules differs from electron interaction due to the difference in polarity of the charge. This makes positrons an alternative tool to study atomic and molecular structure. Recent measurements of the total cross-sections for positron scattering at low energies on He, Ar, H₂, N₂, C₆H₆, C₆H₁₂, C₆H₇N carried out at Trento University [Karwasz et al., Acta Phys. Pol. 127, 666 (2005)] are discussed and compared to electron scattering results. All measured total cross-sections exhibit an increase with decreasing positron energy in the limit of zero energy; H₂, N₂, Ar, show regions of constant cross-section which are a few eV-wide, characteristic of scattering on a hard-sphere potential. Helium shows two resonant structures much below the positronium formation threshold. They may be attributed to virtual positronium formation. In conclusion, positron scattering is complementary to electron scattering. The total cross-sections do not show Ramsuaer minima but constant values, and new resonances appear.