Dissociative Electron Capture by Benzene Derivatives

Abstract

We have studied dissociative electron capture in a series of benzene derivatives using the combined swarm—beam method. The benzene derivatives C₆H₅Cl, o‐C₆H₄Cl₂, o‐C₆H₄CH₃Cl, C₆H₅Br, C₆D₅Br, and o‐C₆H₄CH₃Br, capture low‐energy (including thermal) electrons dissociatively in a capture process which peaks at about 1 eV and yields only Cl⁻ or Br⁻ ions. The energies (in electron volts) at which the capture cross sections σ_c(ε) for the ∼1‐eV processes peak and the values of σ_c(ε) (in cm²×10¹⁷) at peak energy for the above compounds are 0.86, 1.4; 0.36, 43; 1.1, 2.2; 0.84, 9.6; 0.8, 10.4; 0.95, 6 for C₆H₅Cl through o‐C₆H₄CH₃Br, respectively. The rates of capture at thermal electron energies are also given for each compound (but because of impurities are in question). For comparison with the benzene derivatives, C₂H₅Cl was also studied with the swarm—beam method. Beam data are also presented for dissociative electron capture by C₆H₅I, C₆H₅NO₂, and o‐ and m‐C₆H₄CH₃NO₂.