Two-photon photodissociation of NO through Rydberg levels in the 265–278 nm region: Spectra and photofragment angular distributions

The spectroscopy and dynamics of the NO photodissociation through Rydberg levels near 74 000 cm−1 have been investigated following two-photon excitation. The 6dπ−(v=1) and 5sσ(v=3) levels overlap near 74 070 cm−1. Assignment of the rotational transitions for these levels has been aided by the use of the photoproduct angular distributions measured using product imaging techniques. Product imaging was also used to investigate the 8dπ−(v=1) and 5sσ(v=2) regions assigned by previous investigators. In all cases, the major products were N(2D)+O(3P). The angular distributions vary strongly with rotational transition and with the assumed intermediate in the two-photon excitation scheme and can, for the most part, be predicted by calculation. They demonstrate that, for the Rydberg levels examined, the major contribution to the two-photon line strength is a Π intermediate, likely the C 2Π state, with less than a 30% amplitude contribution from either a Σ or Δ intermediate.