Vibrational excitations mediated by a electronic Feshbach resonance 2Eg+ in electron scattering by hydrogen molecules / Excitações vibracionais medidas pela ressonancia de Feshbach eletronica 2Eg+ no espalhamento de eletrons por moleculas de hidrogenio

AUTOR(ES)

Eliane Marques de Oliveira

DATA DE PUBLICAÇÃO

2006

RESUMO

The relationship between Feshbach resonances and electronic excitation is well known in electron scattering by Hydrogen molecules, but still little exploited in the positron scattering case, making interesting, a comparative study. However, before thinking about comparisons, we have to address the question if, in fact, a Feshbach resonance manifests itself in the positron scattering by Hydrogen molecules. This issue is motivated by the fact that recent measured cross sections have not shown the same features presented by our earlier calculated Feshbach resonance in positron-Hydrogen collisions, carried out in the fixed-nuclei approach for the equilibrium internuclear distance, Ro=1.4ao. Our strategy was to calculate cross sections, still in the fixed nuclei approach, for several internuclear distances around Ro. The obtained results suggest that the experimental absence of the resonance is related to the opening of a new electronic channel for R >Ro. For these calculations we have used the Schwinger Multichannel Method (SMC) to obtain the collision parameters (position and width of the resonances) in combination with the Local Complex Potential approach (also known for Boomerang Model), for inclusion of the coupling of the vibrational degrees of freedom. The absence of the resonance for some internuclear distantes prevents the calculation of vibrationally resolved cross sections by positron impact using the local approach. On the other hand, for the electron scattering case, which is also a challange as a theoretical problem, we have carried out the calculation and have found good agreement with available experimental data.

ASSUNTO(S)

excitação vibracional metodo multicanal de schwinger schwinger multichannel method feshbach resonance ressonancia de feshbach vibrational excitation

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