Femtosecond real-time fragmentation dynamics of the nitrobenzene anion reveal the dissociative electron attachment mechanism

The femtosecond real-time dynamics of the nitrobenzene anion (C₆H₅NO₂ ^-) in the excited state have been investigated using a recently developed time-resolved photofragment depletion (TRPD) spectroscopic technique, providing molecular-level insight into the C-N bond dissociation pathway leading to ˙C₆H₅ and NO₂ ^- fragments for the first time. Ultrafast electronic relaxation from the D₂ state, prepared at 2.48 eV, to the ground state (D₀) is followed by statistical unimolecular dissociation, yielding NO₂ ^- with a lifetime (<i>τ</i>) of approximately 294 ps. This behavior stands in stark contrast to the prompt bond rupture typically observed in conventional dissociative electron attachment (DEA) processes, offering deep insight into the energy flow that governs anionic bond dissociation following electron-molecule collisions.