https://doi.org/10.1140/epjd/e2012-20670-y
Regular Article
Reactions and anion desorption induced by low-energy electron exposure of condensed acetonitrile
1
Département de Médecine Nucléaire et Radiobiologie, Faculté de
Médecine, Université de Sherbrooke, Sherbrooke, QC,
J1H 5N4,
Canada
2
Universität Bremen, Institut für Angewandte und Physikalische
Chemie, Fachbereich 2
(Chemie/Biologie), Leobener Straße/NW 2, Postfach 330440,
28334
Bremen,
Germany
a e-mail: swiderek@uni-bremen.de
Received:
18
November
2011
Received in final form:
11
January
2012
Published online:
28
February
2012
Thermal desorption spectrometry (TDS) and electron stimulated desorption (ESD) are employed to investigate mechanisms responsible for the formation of C2H6 in electron irradiated multilayer films of acetonitrile (CH3CN) at 30 K. Using a high sensitivity time-of-flight mass spectrometer, we observe the ESD of anionic fragments H−, CH2-, CH3- and CN−. Desorption occurs following dissociative electron attachment (DEA) via several negative ion resonances in the 6 to 14 eV energy range and correlates well with a “resonant” structure seen in the TDS yield of C2H6 (i.e., at mass 30 amu). It is proposed that C2H6 is formed by the reactions of CH3 radicals generated following DEA to CH3CN which also yields CN−. Between 2 and 5 eV, a second resonant feature is seen in the C2H6 signal. While DEA is observed in the gas phase at these energies, no anion desorption occurs since anionic fragments likely have insufficient kinetic energy to desorb. Since the CH2- ion has not been observed in gas-phase measurements, we propose that it is formed, along with HCN (that is detected in TDS) when dissociation into CH3- and CN is hindered by adjacent molecules.
Key words: Topical issue: Electron/Positron Collision. Guest editors: Michael Brunger, Anne Lafosse, Gaetana Laricchia, Paulo Limao-Vieira and Nigel Mason
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag 2012