Time-resolved dynamics of NO2 in its conical intersection region.

Photodissociation dynamics of NO(2) in its conical intersection region have been explored experimentally on a real-time scale by time-of-flight mass spectrometry. Excited at 400.6 nm and probed by 801.6 nm femtosecond laser pulses, different dynamical behaviors of both the parent ion NO(2)(+) and the fragment ion NO(+) have been observed under parallel and perpendicular pump-probe laser polarization configurations. Distinct oscillations in NO(2)(+) and NO(+) signals are observed when laser polarizations of pump and probe are perpendicular to each other, whereas the oscillations become blurry when the laser polarizations are parallel. The observed transient signals imply that the dissociation mechanism of NO(2) in the A(2)B(2) excited state needed to be reconsidered. On the basis of our observation, Rydberg states play important roles in the ultrafast dissociation dynamics of NO(2).