Quantum Interference in NO2

This paper investigates the origin of a quantum interference observed when NO2 is dissociatively ionized by short pulses of ultraviolet light. We describe time-resolved measurements of NO+, O+, and NO2+ ions produced following the interaction of NO2 with a similar to 70 fs duration pulse centered close to 400 nm and a subsequent time-delayed probe, pulse close to 269, 205, or 400 nm A quantum beat oscillation with a period of 524 fs and I characteristic damping time of 8 ps is observed oil all transient loll signals, We investigate the effect of fulling the central wavelength of the excitation pulse over a 12 nm range, and we discuss the potential importance of three possible multiphoton pathways involving one, two. and three pump photons We conclude that the Ionization pathway responsible For the beat signal is most likely due to a process involving the absorption of two pump photons and two probe photons. This presents in interesting problem with respect to the Interpretation of the mechanism responsible for the quantum interference signature since the electronic states of NO2 reached at the two-photon level are all though. to be extremely short-lived and to dissociate oil a time scale that Is far shorter than the characteristic damping lime of the oscillatory signals We suggest that a possible explanation for the observed dynamics is a associated with a minor dissociation channel of the (2)B-2(2) state of NO2 through its interaction with the longer lived (2)(2)A(1) state.