Evidence of Roaming Dynamics and Multiple Channels for Molecular Elimination in NO3 Photolysis

We report correlated state distributions arising from NO3 photolysis at 588 nm using velocity map ion imaging. State-selected NO images reveal clear evidence for two dissociation pathways for the NOþO2 channel. Vibrationally excited O2 ( Σg , ν= 5-10) is formed in coincidence with low rotational states of NO (Π) in the dominant mechanism. We also observe a small channel consisting of low vibrational levels of O2 ( Σg , ν=0-4) coincident with high NO rotational states. We discuss the results in the context of the recent studies of formaldehyde dissociation and postulate the involvement of roaming-type dynamics. SECTION Dynamics, Clusters, Excited States T he nitrate radical, NO3, plays an important role in atmospheric chemistry, photolyzing in the visible region to yield two product channels NO3 þ hν f NOþO2 ð1Þ