Photoexcitation of the NO dimer below the threshold of the NO(A2Σ+) + NO(X2Π) channel: a photoion and photoelectron imaging study

The photoexcitation of (NO)2 at 242–221 nm is studied by photoion and photoelectron imaging. A broad and structureless absorption band starting at 41,300 ± 300 cm−1 is observed. Ionization via the excited state accesses predominantly a dissociative state of (NO)2+. The broad kinetic energy distribution of the photoelectrons suggests that the excited state has a large valence component in the Franck–Condon region, and that the geometries of the excited neutral state and the dimer ion state differ markedly. We propose that the same ‘bright’ state of mixed valence/Rydberg character is accessed at 242–200 nm, in agreement with preliminary ab initio calculations.