Dissociative electron attachment to fluorinated nitrobenzenes

Low-energy electron attachment to three fluorinated nitrobenzene molecules in the gas phase in the energy range from zero to 10 eV is reported. Non-dissociative and dissociative electron attachment to 3,5-difluoronitrobenzene, 2,3,4-trifluoronitrobenzene and 2,4,6-trifluoronitrobenzene were observed. The experiments were carried out utilizing a trochoidal electron monochromator coupled to a time-of-flight mass spectrometer. Quantum chemical calculations of the major dissociation pathways have been made to compare thermochemical reaction balances with the experimental findings. The most dominant fragmentation channels involve (partial) dissociation of the nitro group, which is influenced by the fluorination of the molecule. In addition to prompt dissociation in the interaction region, slower metastable fragmentation of the nitro groups via loss of a neutral NO was also observed on microsecond timescales. Remarkably, we also observe the formation of the parent anion of 3,5-difluoronitrobenzene at non-thermal energies.