Bond Dissociation Energy of NO with Subwavenumber Precision via State-to-State Resolved Threshold Fragment Yield Spectroscopy.

We report the bond dissociation energy (BDE) of nitric oxide (NO) with subwavenumber precision (±0.20 cm), measured via state-to-state resolved threshold fragment yield spectroscopy. The ground-state dissociation limit, NO(Π) → N(S) + O(P), yields a BDE of 52396.92 ± 0.20 cm (6.496390 ± 0.000025 eV; 626.8064 ± 0.0024 kJ/mol), reducing the uncertainty of prior work by a factor of 50. Combining this result with equally precise BDEs for N, O, CO, NO, and CO, we derive spectroscopically accurate thermochemical benchmarks, including Δ(NO, 0 K), Δ(NO, 0 K), the atomization energy of NO, the ion-pair dissociation energy of NO, the bond dissociation energies of NO, and the reaction energies for seven key processes. The O(P) fragment angular distribution from NO(Π) predissociation provides direct experimental confirmation of spin-orbit interaction with the NO(Π) continuum. These results establish definitive benchmarks for thermochemistry and quantum chemistry, potentially advancing kinetic modeling in atmospheric chemistry, combustion, and NO research.