Two-photon photodissociation of jet-cooled NO₂ near 450 nm. Rotational distributions of NO

The two-photon photodissociation of expansion-cooled NO₂ has been studied using dissociation and simultaneous two-photon l.i.f probing of the nascent NO(X) by a single scanning dye laser in the 428, 450 and 475 nm wavelength range corresponding to the ?(2, 1) ?(1, 0) ?(0, 0) and ?(0, 1) two-photon bands of NO. While the nascent NO formed in the 450 nm region exhibits a Boltzmann-like rotational population distribution, a distinct bimodal distribution is observed in the 475 nm region. Attention is drawn to the possibility that these differences reflect different branching ratios between the O(³P) and O(¹D) dissociation channels and that the branching ratio varies with wavelength and the nature of the intermediate state involved at the one-photon level.