New Rydberg Series in Molecular Oxygen near 500 Å

Abstract

Previously unknown resonances in the continuous photoionization absorption of molecular oxygen have been observed spectroscopically in the 500–600‐Å region, using the NBS 180‐MeV electron synchrotron as a background source. These resonances form four Rydberg series, two converging to a level in O₂⁺ at 24.564 (±0.004) eV, the others converging to a level in O₂⁺ at 24.754 (±0.004) eV. The resonances are caused by high‐lying autoionized states of neutral oxygen; the transitions involve the excitation of an inner σ_u2s electron to outer nsσ or ndπ orbitals. Additionally, this work confirms the LeBlanc analysis of the Hopfield emission bands at 2100 Å, as being due to transitions in O₂⁺.