Multiphoton ionization of NO2: Spectroscopy and dynamics

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Abstract
We have obtained the multiphoton ionization (MPI) spectrum of NO2 in the region from 520 to 420 nm under conditions of moderate pressure (2 Torr) in a static cell and at low pressure with mass resolution in both a flow system and a supersonic molecular beam. Resonance enhancement due to the 3sσ Rydberg state of NO2 at the level of the third photon characterizes the spectrum above 500 nm. Below 490 nm the spectrum is altered by efficient predissociation to NO. We observe the dynamics of this process, as manifested in the MPI spectrum of nascent NO, to depend upon wavelength and pressure, as these parameters affect the partitioning between competing two-phonon photodissociation channels producing NO(X 2π)+O(3P) and NO(X 2π)+O(1D).