Dissociative electron attachment and vibrational excitation ofH2by low-energy electrons: Calculations based on an improved nonlocal resonance model

Abstract

An improved nonlocal resonance model proposed by \ifmmode \check{C}\else \v{C}\fi{}\'{\i}\ifmmode \check{z}\else \v{z}\fi{}ek, Hor\'a\ifmmode \check{c}\else \v{c}\fi{}ek, and Domcke [J. Phys. B 31, 2571 (1998)] is used for the calculation of cross sections of electron dissociative attachment and vibrational excitation of molecular hydrogen by the impact of low-energy electrons in the range of $^{2}\ensuremath{\Sigma}_{u}^{+}$ resonance. The model is based on ab initio data and takes full account of the nonlocality of the effective potential for the nuclear motion. The dissociative attachment cross sections and rate constants are calculated for all target states $(v,J)$ of relevance and compared with other theoretical and experimental data. It is found that the present dissociative attachment cross section calculated under the conditions of the experiment carried out by Schulz and Asundi reproduces the larger of the two values proposed by them, i.e.--$2.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}21}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{2}$. A detailed discussion of the dissociative attachment cross section as a function of the vibrational and rotational target states is given. Very narrow peaks, with a width of $1\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$, are observed in the dissociative attachment cross section for large values of the orbital quantum number $J$. These structures are interpreted as shape resonances in ${\mathrm{H}}^{\ensuremath{-}}+\mathrm{H}$ collision dynamics. It is shown that for large values of $J$ rotational excitation of the hydrogen molecule enhances the dissociative attachment more efficiently than vibrational excitation. The largest dissociative attachment cross section of $28.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{2}$ is obtained for $v=1$ and $J=29$. The process of vibrational excitation will be discussed in a separate paper.