Spin—Orbit Coupling and Electron-Affinity Determinations from Radiative Capture of Electrons by Oxygen Atoms

The radiative capture continuum for the process O0+e→O−+hν is studied in the region of the threshold, 7800–8800 Å. The spectrum is produced in shock-heated vapors of potassium peroxide and rubidium oxide in neon and argon. Individual thresolds are resolved which correspond to the transitions O(3P2)→O−(2P12),O(3P2)→O−(2P32),O(3P1)→O−(2P32), and possibly O(3P0)→O−(2P12). From these thresholds, the electron affinity of the oxygen atom is determined to be 1.478±0.002 eV and the separation of P212,P212 states of O−, 285±15 cm−1, corresponding to a spin—orbit coupling constant of 190±10 cm−1 for the oxygen negative atomic ion.