No abstract

The dissociative electron attachment (DEA) process to water (H 2 O) and heavy water (D 2 O) has been studied in the gas phase in a cross beam experiment for electron energies up to 20 eV. The apparatus used eliminates discrimination due to the kinetic energy and angular distribution of the ions. The cross sections are normalized to absolute values using the cross section for production of O − from O 2 (Rapp and Briglia 1965 J. Chem. Phys. 43 1480). These are the first exhaustive measurements of absolute cross sections for both the H − and O − from H 2 O and D − and O − from D 2 O at all the three resonances. The results are compared with the scarce data available in the literature. Isotope effect is observed at the 12 eV resonance in the H − channel and at all the three resonances in the O − channel.

Gas phase chemistry in the cold interstellar clouds is dominated by ion-molecule and radical-radical interactions, though some neutralneutral reactions are also barrier-free and efficient at cold temperatures. It has been suggested that it is impossible to synthesize detectable abundances of the pre-biotic HCN oligomer adenine (H 5 C 5 N 5 ) in the interstellar medium via successive neutral-neutral reactions. We attempted therefore to use quantum chemical techniques to explore if adenine can possibly form in the interstellar space by radical-radical and radical-molecule interaction schemes, both in the gas phase and in the grains. We report results of ab initio calculations for the formation of adenine starting from some of the simple neutral molecules and radicals detected in the interstellar space. The reaction path is found to be totally exothermic and barrier free, which increases the probability of occurrence in the cold interstellar clouds (10−50 K). We also estimated the reaction rates.

We present a joint theoretical-experimental study on electron scattering by propane (C 3 H 8) in the low-and intermediate-energy ranges. Calculated elastic differential, integral, and momentum transfer as well as total (elastic + inelastic) and total absorption cross sections are reported for impact energies ranging from 2 to 500 eV. Also, experimental absolute elastic cross sections are reported in the 40-to 500-eV energy range. A complex optical potential is used to represent the electron-molecule interaction dynamics. A theoretical method based on the single-center-expansion close-coupling framework and corrected by the Padé approximant is used to solve the scattering equations. The experimental angular distributions of the scattered electrons are converted to absolute cross sections using the relative flow technique. The comparison of our calculated with our measured results, as well as with other experimental and theoretical data available in the literature, is encouraging.

In this work, we present a joint theoretical and experimental study on electron-H 2 S collisions in the low-and intermediate-energy range. More specifically, we report measured elastic differential, integral, and momentumtransfer cross sections in the ͑100-500͒-eV energy range. In addition, calculated elastic cross sections in the ͑0.5-500͒-eV energy range are also reported. The measurements were performed using a crossed electron beam-molecular beam geometry. The angular distributions of the scattered electrons were converted to absolute cross sections using the relative flow technique. Theoretically, an optical potential is used to represent the electron-molecule interaction. The Schwinger variational method combined with the distorted-wave approximation is used to solve the scattering equations. The comparison between our calculated and measured results as well as with other available experimental and theoretical data in the literature is encouraging.

No abstract

We present a joint theoretical-experimental study on electron scattering by ethane (C 2 H 6 ) in the low-and intermediate-energy ranges. Calculated elastic differential, integral and momentum transfer as well as total (elastic + inelastic) and total absorption cross sections are reported for impact energies ranging from 1 to 500 eV. Also, experimental absolute elastic cross sections are reported in the 40-500 eV energy range. A complex optical potential is used to represent the electron-molecule interaction dynamics. A theoretical method based on the single-centre-expansion close-coupling framework and corrected by the Padé approximant technique is used to solve the scattering equations. The experimental angular distributions of the scattered electrons are converted to absolute cross sections using the relative flow technique. The comparison of our calculated results with our measured results, as well as with other experimental and theoretical data available in the literature, is encouraging.

No abstract