title: Dynamics of highly excited nitroaromatics.
abstract: Although the photodissociation of nitroaromatics in low excitation electronic states has been extensively studied in recent decades, little is known about the highly excited electronic states. The fragmentation dynamics of three nitroaromatics, nitrobenzene, o-nitrotoluene, and m-nitrotoluene, in highly excited states, populated by the absorption of two photons at 271 nm, are studied with time-of-flight mass spectrometry. The temporal evolutions of the highly excited states are monitored by one-photon ionization at 408 nm. The transients of parent and fragment ions exhibit two ultrafast deactivation processes. The first process is ultrafast internal conversion from the initial excitation to Rydberg states in tens of femtoseconds. The second one is conversion from the Rydberg states to the vibrational manifold in the ground electronic states within hundreds of femtoseconds. The internal conversion process is accelerated by methyl substitution. In o-nitrotoluene, the two processes become much faster due to the hydrogen transfer from the CH(3) to the NO(2) group (ortho effect).
authors.affiliation: State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Dalian 116023, China.
authors.forename: Bingxing
authors.initials: B
authors.lastname: Wang
authors.forename: Benkang
authors.initials: B
authors.lastname: Liu
authors.forename: Yanqiu
authors.initials: Y
authors.lastname: Wang
authors.forename: Li
authors.initials: L
authors.lastname: Wang