Electron Attachment to Aliphatic Hydrocarbons of the Form n-CNH2N+1Br(N = 2–6 and 8) II. A Swarm-Beam Study

A swarm-beam study has been made of brominated hydrocarbons of the form n-CNH2N+1Br(N = 2–6 and 8). At energies below ∼ 3 eV the abundant ion found in the beam study was Br−. The dissociative attachment cross section σda(ε) peaked at 0.76, 0.74, 0.73, 0.70, 0.71, and 0.13 eV, and had peak values equal to 3.95, 4.14, 5.50, 6.13, 7.41, and 32.2 × 10−18 cm2 for N = 2–6 and 8, respectively. A small decrease has been observed in the cross-section width with increasing reduced mass Mr of the R(= n − CNH2N+1)–Br molecules. This and the increase in σda with Mr are discussed within the resonance-scattering-theory treatment of dissociative electron attachment to diatomic molecules. For some of the molecules studied, potential energy diagrams for RBr and RBr−* and separation and autoionization lifetimes for RBr−* are given.