Dissociative electron attachment resonances in ammonia: A velocity slice imaging based study

• Published in: The Journal of chemical physics 2012-04, Vol.136 (16), p.164308-164308-7
• Main Authors: Ram, N. Bhargava, Krishnakumar, E.
• Format: Article
• Language: English
• Subjects: Ammonia; Ammonia - chemistry; Angular distribution; Angular velocity; Anions; Asymmetry; Channels; Electrons; Fragmentation; Kinetic energy; Kinetics
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.4705358

Negative ion resonance states of ammonia are accessed upon capture of electrons with energy 5.5 eV and 10.5 eV, respectively. These resonance states dissociate to produce H − and \documentclass[12pt]{minimal}\begin{document}${\rm NH}_2^-$\end{document} NH 2 − fragment anions via different fragmentation channels. Using the velocity slice imaging technique, we measured the angular and kinetic energy distribution of the fragment H − and \documentclass[12pt]{minimal}\begin{document}${\rm NH}_2^-$\end{document} NH 2 − anions with full 0-2π angular coverage across the two resonances. The scattered H − ions at both resonances show variation in their angular distribution as a function of the kinetic energy indicating geometric rearrangement of \documentclass[12pt]{minimal}\begin{document}${\rm NH}_3^{-*}$\end{document} NH 3 − * ion due to internal excitations and differ from the equilibrium geometry of the neutral molecule. The second resonance at 10.5 eV shows strong forward-backward asymmetry in the scattering of H − and \documentclass[12pt]{minimal}\begin{document}${\rm NH}_2^-$\end{document} NH 2 − fragment ions. Based on the angular distributions of the H − ions, the symmetry of the resonances at 5.5 eV and 10 .5 eV are determined to be A 1 and E, respectively, within C 3 v geometry.