Associative and dissociative electron attachment by SF6 and SF5Cl

Abstract

Electron attachment by SF6 and SF5Cl in the energy range 0–20 eV has been studied in a beam experiment at room temperature. At low energies (≊0 eV) electron attachment to SF6 yields the well known parent anion SF−*6 (associative attachment) and SF−5 (dissociative attachment), while other negative ion fragments (F−, F−2 , SF−2 , SF−3 , and SF−4) are generated with comparably low cross sections from various resonances at higher energies. In contrast to that, negative ion formation in SF5Cl is dominated by dissociative channels (F−, Cl−, FCl−, and SF−5 ) and only a weak SF5Cl− signal is observed. A time-of-flight analysis of the ionic fragments reveals that the decomposition of all resonances is characterized by a low translational excess energy release indicating effective energy randomization in the parent ion prior to dissociation. The present results are compared with negative ion formation in halogenated hydrocarbons.