Dissociation dynamics of 3- and 4-nitrotoluene radical cations: Coherently driven C$-$NO$_2$ bond homolysis

摘要: Monosubstituted nitrotoluenes serve as important model compounds for nitroaromatic energetic molecules such trinitrotoluene. This work investigates the ultrafast nuclear dynamics of 3- and 4-nitrotoluene radical cations using femtosecond pump-probe measurements results density functional theory calculations. Strong-field adiabatic ionization 1500 nm, 18 fs pulses produces in ground electronic state with distinct coherent vibrational excitations. In both nitrotoluene isomers, a one-photon excitation probe pulse \ce{NO2} loss to form \ce{C7H7+}, which exhibits out-of-phase oscillations yield parent molecular ion. The period 470 are attributed torsional motion group based on theoretical showing that dominant relaxation pathway cation involves rotation away from planar geometry. distinctly faster oscillation 216 3-nitrotoluene is an in-plane bending \ce{CH3} moieties analysis normal modes. These demonstrate motions determine probability \ce{C-NO2} homolysis upon optical within several hundred femtoseconds initial event.