Temperature dependence of electron attachment to CHCLBr2: crossed beams study

Abstract

Dissociative electron attachment (DEA) to CHClBr2 has been studied in a crossed electron/molecular beams experiment in the electron energy range between 0 and 8eV and in the gas temperature range from 321 to 475K. In this electron energy range we have found two negative fragment ions Cl− and Br− which are formed from a prominent low energy resonant feature (∼0eV) and at resonances at about 0.4 and 4.7eV. The molecular ion ClBr−, in contrast to the swarm experiment, was not observed in the beam experiment. The total absolute cross-section for DEA has a value of 1.4(±0.2)×10−20m2 at 0.4eV and 5(±2)×10−22m2 at 4.7eV. The total DEA cross-section and the DEA cross-section for Br− reaction channel are temperature independent at low electron energies (∼0eV). The cross-section for Cl− reaction channel at ∼0eV increases with the gas temperature and for this reaction channel we have derived activation energy of 42(±15)meV. The enthalpies of the DEA reaction and CCl and CBr bonds have been calculated at G2MP2 and G2 level of theory. The DEA reaction has been found exothermic for both reaction channels.