INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF PHYSICS B: ATOMIC, MOLECULAR AND OPTICAL PHYSICS J. Phys. B: At. Mol. Opt. Phys. 36 (2003) 443–452 PII: S0953-4075(03)54951-3 A study of dissociative electron attachment to CHBr 3 and CHI 3 M Stano 1 , V Foltin 1 , S Matejcik 1,3 , J Langer 2 , S Gohlke 2 and E Illenberger 1,2 1 Department of Plasma Physics, Comenius University, Mlynska dolina F2, 84248 Bratislava, Slovak Republic 2 Institut f¨ ur Chemie, Physikalische und Theoretische Chemie, FU Berlin, Takustraße 3, 14195 Berlin, Germany E-mail: matejcik@fmph.uniba.sk Received 7 October 2002, in final form 28 November 2002 Published 22 January 2003 Online at stacks.iop.org/JPhysB/36/443 Abstract Dissociative electron attachment (DEA) has been studied in the systems Br − /CHBr 3 and I − /CHI 3 in a crossed electron/molecular beams experiment in the electron energy range from about 0 to 10 eV. In addition to prominent low- energy resonances (also observed in previous studies), we find a resonance in the system Br − /CHBr 3 at 4.65 eV and we find three additional resonant features in the system I − /CHI 3 at 2.1, 2.9 and 4.1 eV. The absolute partial cross-section for the Br − /CHBr 3 DEA reaction was estimated as (3 ± 1) × 10 −17 cm 2 at 0.5 eV and (2 ± 1) × 10 −18 cm 2 at 4.65 eV. Analysis of the energy dependence of the I − /CHI 3 cross-section reveals s-wave attachment near threshold (≈0 eV) and an additional pronounced feature located at 58 meV. We tentatively assign this feature to vibrational Feshbach resonance associated with excitation of the ν 2 vibrational quanta of CHI 3 . (Some figures in this article are in colour only in the electronic version) 1. Introduction Dissociative electron attachment (DEA) to molecules is a reaction relevant in many fields of pure and applied science (electrical discharges, plasmas, atmospheric chemistry, interstellar chemistry, radiation chemistry etc). Halogenated hydrocarbons belong to the group of gases showing the best electron attachment. The halogenated methanes have been the subject of extensive swarm and crossed beam studies [1]. The haloforms CHX 3 (where X stands for a halogen atom) constitute a special class of the halo-methanes. While fluoroform (CHF 3 ) [2–6] and chloroform [7–10] have been studied in a large number of crossed beam and swarm studies, 3 Author to whom any correspondence should be addressed. 0953-4075/03/030443+10$30.00 © 2003 IOP Publishing Ltd Printed in the UK 443