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 p* 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*Ó → 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.