Temporary anion states and dissociative electron attachment to nitrobenzene derivatives

The nitrobenzene derivatives 1,2-nitrotoluene, 1,3-nitrotoluene, 1,2-fluoronitrobenzene, 1,3-fluoronitrobenzene, 1,4-fluoronitrobenzene, 1,2-chloronitrobenzene, 1,3-chloronitrobenzene and 1,4-chloronitrobenzene are investigated by means of electron transmission spectroscopy (ETS), dissociative electron attachment spectroscopy (DEAS) and negative ion mass spectrometry (NIMS). The observed energies of electron attachment to π* MOs were interpreted with the support of the empty level structures of the neutral molecules supplied by HF/6-31G and B3LYP/6-31G* calculations. In the chlorine-substituted derivatives three main long-lived negative ions (NIs) (M−, Cl−, and NO2−) are observed, only M− and NO2− in the other investigated compounds. The detection of the metastable NIs corresponding to the process M*− → R− + (M–R) suggests that the molecular NIs formed near thermal electron energy dissociate on a microsecond timescale. Mean autodetachment lifetimes of the molecular NIs as a function of electron energy are evaluated.