Laser photodissociation of O3− by triple quadrupole mass spectrometry

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Abstract
Absolute cross sections for the production of both O− and O2− by photodissociation of O3− have been determined at intervals of 0.2 nm or less throughout the range from 380 to 650 nm. The results indicate that both the 2A2 and the 2A1 excited state are accessible in this range. Threshold energies and vibrational assignments are derived from the data. For the transition 2A2←2B1, T00 = 2.046±0.002 eV, υ1′ = 815±10 cm−1, υ2′ = 275±10 cm−1, υ1′′ = 975±10 cm−1, υ2′′ = 590±10 cm−1; for 2A1←2B1, T00 = 2.655 eV, υ1′ = 760±20 cm−1, υ2′ = 190±20 cm−1. The threshold for O2− production is interpreted to yield D(O–O2−)?2.41±0.01 eV, which together with other recent spectroscopic determinations of pertinent thermochemical quantities implies that D(02–O−)?1.388±0.013 eV and D(O2–O)?0.747±0.013. The latter value is in serious disagreement with the literature value of 1.05±0.02 eV determined calorimetrically but is in good agreement with results derived from recent spectroscopic measurements on the positive and negative ions of ozone.