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

G.P. Karwasza, R.S. Brusab, D. Pliszkac, Z. Idziaszekd and H. Nowakowskae aInstitute of Physics, Nicolaus Copernicus University, Grudziądzka 5/7, 87-600 Toruń, Poland bPhysics Department, Trento University, Sommarive 14, 38050 Trento, Italy cInstitute of Physics, Pomeranian Pedagogical Academy, 76-200 Słupsk, Poland dCNR-INFM BEC Center, 38050 Trento Italy and Center of Theoretical Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warszawa, Poland eInstitute of Fluid Flow Machinery, Polish Academy of Sciences, Fishera 14, 80-952 Gdańsk, Poland

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Received: 5 06 2006;

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 virtual-positronium model, developed recently by Gribakin, reproduces a constant dependence of the total cross section in a few eV energy range.

DOI: 10.12693/APhysPolA.110.605 PACS numbers: 34.85.+x, 39.90.+d