Positron Scattering on Atoms and Molecules in the Limit of Low Energy

Abstract

Starting from experimental cross-sections for positron scattering in argon and nitrogen, we examine different energy ranges. In the zero-energy limit the cross-section falls with energy and can be described by modified effective range theory for polarization potential. In a few eV range the cross-sections are constant vs. energy. As far as it is possible to force the elastic scattering phase shifts in a way that both experimental differential cross-sections are reproduced and the total cross-section remains constant in energy, such a model lacks the physical justification. Only the virtualpositronium model, developed recently by Gribakin, reproduces a constant dependence of the total cross-section in a few eV energy range.

Improving the wavefunction of the Schwinger multichannel method for positron scattering—II: Application for elastic and inelastic e+-H2 scattering

“…direct annihilation and formation processes. The comprehension of these elastic and inelastic processes may be very useful in the near future to create alternative techniques of producing positron beams (to cite positron-molecule collisions is a controversial area and several considerations have been discussed [5][6][7][8][9][10][11][12]). A suitable theoretical method should be capable of dealing with several important aspects of the problem such as polarization effects, resonances, electronically inelastic scattering with several open and closed channels, positronium formation and, if possible, with computer codes applicable to targets in general.…”

A rigid sphere approach to positron elastic scattering by noble gases, molecular hydrogen, nitrogen and methane

“…Recently, in more detailed study [10] we showed that the atomic radii dea e-mail: kamil@fizyka.umk.pl termined from positron scattering data using a classical rigid sphere model are comparable to covalent radii of atoms. However this simple picture does not translate directly into the quantum mechanics since pure quantummechanical hard-sphere model is not applicable to lowenergy positron scattering [11].…”