title: Temperature effects on the dissociative electron attachment to dichlorobenzene isomers.
abstract: Dissociative electron attachment to all three isomers of dichlorobenzene has been investigated in the electron energy range from 0 to 2 eV and in the gas temperature range from 391 to 696 K using a crossed electron-molecular beam apparatus with a new temperature-regulated effusive molecular beam source. In the case of the dissociative electron attachment channel Cl(-)/1,2-dichlorobenzene and Cl(-)/1,4-dichlorobenzene, strong enhancement of the negative ion production with the gas temperature at low electron energies has been observed. The low-energy peak increases dramatically when the gas temperature is raised from 391 to 696 K. Activation energies for dissociative electron attachment of (482 +/- 20) meV for 1,2-dichlorobenzene and (59 +/- 20) meV for 1,4-dichlorobenzene have been determined. For the resonance at (0.49 +/- 0.03) eV in 1,2-dichlorobenzene and (0.32 +/- 0.03) eV in 1,4-dichlorobenzene, no dependence of the cross sections on the gas temperature has been observed. In the case of the dissociative electron attachment to Cl(-)/1,3-dichlorobenzene, the cross section does not depend on the temperature in the electron energy range from 0 to 2 eV. Quantum chemical calculations of the reaction energies and of the potential energy curves involved in the dissociation of Cl(-) have been performed, together with an analysis of the thermo dynamical accessibility of the relevant vibrational modes. Possible reasons for the different temperature dependences of the isomers are discussed.
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Mahmoodi-Darian
authors.forename: A
authors.initials: A
authors.lastname: Mauracher
authors.forename: A
authors.initials: A
authors.lastname: Aleem
authors.forename: S
authors.initials: S
authors.lastname: Denifl
authors.forename: B
authors.initials: B
authors.lastname: Rittenschober
authors.forename: A
authors.initials: A
authors.lastname: Bacher
authors.forename: M
authors.initials: M
authors.lastname: Probst
authors.forename: T D
authors.initials: TD
authors.lastname: Märk
authors.forename: P
authors.initials: P
authors.lastname: Scheier