Dissociative Electron Attachment to Formamide: Direct and Indirect Pathways from Resonant Intermediates T. P. M. Goumans, † F. A. Gianturco,* ,‡ F. Sebastianelli, ‡ I. Baccarelli, § and J. L. Rivail | Department of Chemistry, UniVersity College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom, Department of Chemistry and CNISM, UniVersity of Rome La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy SuperComputing Center CASPUR, Via dei Tizii 6, 00185 Rome, Italy, and Laboratoire de Chimie Theorique, UniVersite ´ Henri Poincare, F54506 VandoeuVre-les-Nancy, France Received September 9, 2008 Abstract: Dissociative electron attachment (DEA) to formamide (HCONH 2 ), the smallest molecule with a peptide bond, is investigated with electron-molecule scattering calculations. At the equilibrium geometry we identify two resonances of A′′ and A′ symmetry at 3.77 and 14.90 eV, respectively. To further assess potential bond-breaking pathways for the transient negative ions (TNIs), the behavior of the resonances upon bond stretching of the C-H and C-N bond is investigated. While along the C-H dissociation coordinate neither resonance changes significantly, we find instead that both resonances are stabilized upon stretching the peptide C-N bond, with their resonance energy and width coming down rapidly, most strongly so for the A′ resonance. The A′ resonance is thus seen to disappear when the C-N bond is stretched for more than 1 Å, where it presumably smoothly connects to a bound anion state, a direct DEA pathway for the A′ TNI to yield NH 2 - and HCO. The A′′ resonance is found instead not to be purely dissociative along the C-N coordinate but to evolve into forming a low-lying resonance on the NH 2 fragment. Furthermore, symmetry considerations dictate here that the incoming electron attaches itself to an orbital of A′ symmetry of the NH 2 - and HCO asymptotic fragments. Therefore, DEA from the A′′ TNI has to occur via a symmetry-breaking, nonadiabatic curve crossing which connects to the purely dissociative A′ metastable anionic state that is coming down in energy as the bond stretching occurs. 1. Introduction The chemistry of low-energy electrons (LEEs) is currently actively investigated in view of its important role in radiation-induced damage to biomolecules 1-14 and in the processing of interstellar ices by cosmic rays. 15-23 The primary ionizing events are known to generate large amount of secondary electrons in the range of 0-20 eV 24 which can then resonantly attach themselves to molecular targets and yield formation of transient negative ions (TNIs). The energized TNI, in turn, could either evolve by autodetaching the extra electron or could dispose of the excess energy within its molecular framework, a path which may ultimately lead to rupture of a chemical bond within the target: this process, yielding a stable anion and a radical fragment, is known as dissociative electron attachment (DEA). Here we study the resonances of formamide and its potential DEA pathways by using electron-molecule quantum scattering calculations. With similar methods, DEA processes in glycine, 11 uracil, 3 and formic acid 4 have been studied, while quantum dynamics coupled to quantum chemistry calculations have been used to study DEA in the sugar-DNA backbone. 5 * Corresponding author e-mail: fa.gianturco@caspur.it. † University College London. ‡ University of Rome La Sapienza. § SuperComputing Center CASPUR. | Universite ´ Henri Poincare. J. Chem. Theory Comput. 2009, 5, 217–221 217 10.1021/ct800379h CCC: $40.75  2009 American Chemical Society Published on Web 12/05/2008