Optical Selection in Double-Resonant Two-Photon Photodissociation: Near-Threshold State-to-State Fragmentation Dynamics of NO2 + 2hν --> NO(X 2Π1/2, v = 0, J, Λ) + O(1D)

Article abstract of DOI:10.1021/j100272a056

Optical-optical double resonance is employed to achieve state-to-state resolution in two-photon photodissociation.NO2 seeded in a free-jet expansion is dissociated by sequential two-photon absorption in the region of 488 nm, just above the theresold for production of O(¹D).The channel to produce excited oxygen is observed to dominate the formation of vibrationally cold NO(X ²Π, v = 0), which is detected by resonant two-photon ionization.For two-photon photolysis energies within 100 cm^-1 of threshold, photodissociation dynamics, manifested in NO rotational and Λ-doublet state distributions, are observed to be a sensitive function of parent intermediate state.NO populations are an oscillatory function of J, with varying patterns of Λ-doublet preference that change with selected NO2 intermediate state.Certain features in the photodissociation spectrum of NO2 in this region are seen to correlate with product NO state total parity.At energies higher above threshold (>200 cm^-1), the oscillatory behavior in J is less pronounced and, accordingly, less sensitive to total photolysis energy.In this region a uniform Λ-doublet preference also emerges.