Anomalous behaviour in NO–Ar (Ã) photodissociation near threshold: A significant contribution from thermally populated states

Dissociation of NO–Ar (Ã) with 50 cm–1 excess energy produces NO rotational states that are not allowed energetically. Translational energy distributions for these products reveal that states up to the X ˜ state dissociation energy (88 cm−1) are being excited to the à state and contribute to the observed dissociation. Translational energy distributions for the ‘energetically allowed’ rotational states also show a contribution from these thermally populated states. Dissociation from à levels accessed from thermally populated X ˜ states accounts for 40% of the products observed. The translational energy distributions reveal the shape of the NO–Ar à state population distribution produced, which is a product of the X ˜ state thermal distribution and Franck-Condon factors.