Elastic positron scattering by C{sub 2}H{sub 2}: Differential cross sections and virtual state formation
- Instituto de Ciencias Exatas e Tecnologica, Universidade Paulista, Unip, 13043-900 Campinas, Sao Paulo (Brazil)
We present calculated elastic differential cross sections for positron-acetylene scattering, obtained by using the Schwinger multichannel method. Our results are in very good agreement with quasielastic experimental data of Kauppila et al. [Nucl. Instrum. Meth. Phys. Res. B 192, 162 (2002)]. We also discuss the existence of a virtual state (zero-energy resonance) in e{sup +}-C{sub 2}H{sub 2} collisions, based on the behavior of the integral cross section and of the s-wave phase shift. As expected the fixed-nuclei cross section and annihilation parameter (Z{sub eff}) present the same energy dependence at very low impact energies. As the virtual state energy approaches zero, the magnitude of both cross section and Z{sub eff} are extremely enhanced (at zero impact energy). The possibility of shifting from a low-lying virtual state to a shallow bound state is not expected to significantly affect room-temperature annihilation rates.
- OSTI ID:
- 20640487
- Journal Information:
- Physical Review. A, Vol. 68, Issue 6; Other Information: DOI: 10.1103/PhysRevA.68.062706; (c) 2003 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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