Electron impact induced anion production in acetylene

Abstract

A detailed experimental investigation of electron induced anion production in acetylene, C₂H₂, in the energy range between 1 and 90 eV is presented. The anions are formed by two processes in this energy range: dissociative electron attachment (DEA) and dipolar dissociation (DD). DEA in C₂H₂ is found to lead to the formation of H⁻ and C₂⁻/C₂H⁻ through excitation of resonances in the electron energy range 1–15 eV. These anionic fragments are formed with super thermal kinetic energy and reveal no anisotropy in the angular distributions. DD in C₂H₂ leads to the formation of H⁻, C⁻/CH⁻ and C₂⁻/C₂H⁻ with threshold energies of 15.7, 20.0 and 16.5 eV respectively. The measured anion yields have been used to calculate anion production rates for H⁻, C⁻/CH⁻ and C₂⁻/C₂H⁻ in Titan's ionosphere.