PICOSECOND RESOLUTION MEASUREMENTS OF NO3 UNIMOLECULAR DECOMPOSITION - THE NO+O2 CHANNEL

The title reaction has been studied with picosecond resolution at energies near threshold. Expansion cooled nitrate radicals were photoexcited to admixtures of 2E' and ground state 2A2' levels, ensuring a unimolecular decomposition mechanism. NO was monitored by LIF. The dissociation rate is almost-equal-to 1 X 10(9) s-1 just above the 16800 cm-1 NO+O2 barrier and increases rapidly with energy, reaching 5.5 X 10(9) s-1 at 17040 cm-1. A marked signal decrease at higher energies is attributed to NO2+O dominating above its thermodynamic threshold. These observations support three-center NO+O2 formation via 2A2'.