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|Type:||Artigo de periódico|
|Title:||Comparative Study Of Electron And Positron Scattering By H2: The Role Of The Σg+2 Feshbach Resonance|
|Author:||De Oliveira E.M.|
|Abstract:||We report two-channel calculations for e± - H2 scattering (X Σg+1 →X Σg+1, B Σu+3 for electrons and X Σg+1 →X Σg+1, B Σu+1 for positrons). We provide independent estimates of the electron Σg+2 Feshbach resonance (though for a limited range of interatomic distances) in good agreement with benchmark calculations. Resonance enhanced vibrational excitation cross sections were obtained with a time-dependent local complex potential approach and compare favorably with recent calculations and experimental data. The time resolution also provides good physical insight into the transient dynamics. In a previous work, we predicted the existence of a positron-hydrogen Σg+2 Feshbach resonance based on a fixed-nuclei scattering calculation (equilibrium geometry) that was not observed experimentally. We further investigate the resonance potential in this study and our results indicate that the Σg+2 potential crosses the B Σu+1 state just above the equilibrium interatomic distance of the ground state, giving rise to a short-lived transient. Though the positronium formation channel could also play a role, the state crossing sheds light on the controversy between theory and experiment. © 2008 The American Physical Society.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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