Binary-encounter dipole model for positron-impact direct ionization
| Autor: | Kamil Fedus, Grzegorz P. Karwasz |
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| Rok vydání: | 2019 |
| Předmět: | |
| Zdroj: | Physical Review A. 100 |
| ISSN: | 2469-9934 2469-9926 |
| DOI: | 10.1103/physreva.100.062702 |
| Popis: | In the present work we study the applicability of the binary-encounter-dipole (BED) model and its simpler version the binary-encounter-Bethe model for positron-impact direct ionization. We show that ignoring the exchange and interference effects in the theory of Kim and Rudd [Phys. Rev. A 50, 3954 (1994)] yields simple analytical formulas with no fitting parameters that can be used to estimate cross sections over a wide energy range except near-threshold region. To correct this deficiency we combine BED theory with the Wannier-type threshold law derived by Klar [J. Phys. B 14, 4165 (1981)] for positron-impact ionization. We show that such combination is necessary in order to predict cross sections at low positron energies where strong polarization-correlation effects are present during collision and the positronium formation is a dominant scattering process. The present theory is tested for a wide range of targets including helium (He), atomic hydrogen (H), neon (Ne), argon (Ar), molecular hydrogen (${\mathrm{H}}_{2}$), nitrogen (${\mathrm{N}}_{2}$), oxygen (${\mathrm{O}}_{2}$), carbon monoxide (CO), carbon dioxide (${\mathrm{CO}}_{2}$), and methane (${\mathrm{CH}}_{4}$). An extensive comparison with available experiments and theories is done. |
| Databáze: | OpenAIRE |
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