Dissociative electron attachment to formamide

Formamide (HCONH2) is the smallest molecule with a peptide bond and has recently been observed in the interstellar medium (ISM), suggesting that it may be ubiquitous in star-forming regions. There is therefore considerable interest in the mechanisms by which this molecule may form. One method is electron induced chemistry within the icy mantles on the surface of dust grains. In particular it has been recently shown that functional group dependence exists in electron attachment processes giving rise to site selective fragmentation of molecules at the C-H, O-H and N-H bonds at energies well beyond the threshold for the breaking of any of these bonds allowing novel forms of chemistry that have little or no activation barriers, such as are necessary in the ISM. In this poster we present the results of resent studies on dissociative electron attachment (DEA) to formamide DEA using an improved version of a Velocity Map Imaging (VMI) spectrometer comprised of a magnetically collimated and low energy pulsed electron gun, a Faraday cup (to measure the incident current), an effusive molecular beam, a pulsed field ion extraction, a time of flight analyzer and a two-dimensional position sensitive detector consisting of microchannel plate and a phosphor screen. The VMI spectrometer measures the kinetic energy and angular distribution of the fragment anions produced in the dissociative electron attachment process. The kinetic energy measurements provide information on the internal energies of the fragment anions and determine the dissociation limits of the parent negative ion resonant states responsible for the dissociative electron attachment process. The angular distribution measurements provide the information about the symmetry of these negative ion resonant states. We shall present the details, results and conclusions of these measurements during the conference

Dissociation dynamics of transient anion formed via electron attachment to sulfur dioxide

We report the molecular dynamics of dissociative electron attachment to sulfur dioxide (SO2) by measuring the momentum distribution of fragment anions using the velocity slice imaging technique in the electron energy range of 2–10 eV. The S- channel results from symmetric dissociation which exhibits competition between the stretch mode and bending mode of vibration in the excited parent anion. The asymmetric dissociation of parent anions leads to the production of O- and SO- channels where the corresponding neutral fragments are formed in their ground as well as excited electronic states. We also identify that internal excitation of SO- is responsible for its low yield at higher electron energies

Dissociative Electron Attachment Cross Sections for H₂ and D₂

New measurements of the absolute cross sections for dissociative electron attachment (DEA) in molecular hydrogen and deuterium are presented which resolve previous ambiguities and provide a test bed for theory. The experimental methodology is based upon a momentum imaging time-of-flight spectrometer that allowed us to eliminate any contributions due to electronically excited metastable neutrals and ultraviolet light while ensuring detection of all the ions. The isotope effect in the DEA process in the two molecules is found to be considerably larger than previously observed. More importantly, it is found to manifest in the polar dissociation process (also known as ion pair production) as well