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An electron swarm study has been made of brominated aliphatic hydrocarbons of the form n-CNH2N+1Br(N = 1–6, 8, and 10). Attachment rates, αw, as a function of mean electron energy 〈ε〉, are reported. The attachment rates reach a maximum value at ≤ 0.038, 0.76, 0.76, 0.75, 0.74, 0.73, 0.20, and ≤ 0.038 eV for N = 1 to 6, 8, and 10, respectively. The observed variation in both the magnitude of αw and in the widths of the αw vs 〈ε〉 functions within this series of molecules are discussed within the resonance scattering theory. In addition to a dissociative electron attachment process yielding Br− via a short-lived (< 10−13 sec) compound negative ion state, another electron attachment process involving a longer-lived (∼ 10−10–10−6 sec) state is suggested by the data. For the fast process leading to Br− production, these molecules can be considered as diatomiclike R(=CNH2N+1)–Br systems. The cross sections for the CH3Br and n-C10H21Br molecules reach a maximum value at energies < 3 / 2kT. Over the energy range from 3 / 2kT to ∼ 0.8 eV the cross section for n-C10H21Br can be represented by Aγε−γ, where ε is the electron energy in electron volts, Aγ is equal to 3.5 × 10−18 (eV)γ·cm2, and γ is equal to 1.398. Attachment rates as a function of 〈ε〉 are reported also for some chlorinated aliphatic compounds including CCl4 for which the attachment cross section over the energy range from 3 / 2kT to 0.6 eV can be approximated also by Aγε−γ with Aγ = 3 × 10−16 (eV)γ·cm2 and γ = 1.226. The data presented in this paper distinctly demonstrate the potential of the electron swarm method in electron attachment studies.

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The first optically enhanced electron attachment involving electronically excited molecules is reported. The metastable (triplet) states responsible for the photoenhanced electron attachment were produced indirectly via internal conversion from higher excited singlet states which are strongly optically allowed and are reached by excimer-laser excitation.P T -133 kPa /