Details

Autor(en) / Beteiligte

• Ampadu Boateng, Derrick
• Gutsev, Gennady L.
• Jena, Puru
• Tibbetts, Katharine Moore

Titel

Dissociation dynamics of 3- and 4-nitrotoluene radical cations: Coherently driven C–NO2 bond homolysis

Ist Teil von

• The Journal of chemical physics, 2018-04, Vol.148 (13), p.134305-134305

Ort / Verlag

United States: American Institute of Physics (AIP)

Erscheinungsjahr

2018

Quelle

American Institute of Physics (AIP) Journals

Beschreibungen/Notizen

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