Absorption Cross Sections of O₂(a¹Δg) and O₂(X³Σg⁻) in the Region from 1087 to 1700 Å

An attempt has been made to measure the absorption cross sections of O 2 in the metastable state a 1 Δ g from 1087 to 1700 Å. The absorption is measurable (σ a ≥ 3 × 10 −19 cm 2 ) from around 1500 Å towards shorter wavelengths. Many band structures overlaying various continua have been seen. Absorption cross sections of O 2 in the ground state X 3 Σ g − also have been measured in the same wavelength region and our results agree with previously published values within experimental error. The cross sections of O 2 (a 1 Δ g ) are generally larger than those of O 2 (X 3 Σ g − ) below 1290 Å except at the wavelengths of a few strong bands of O 2 (X 3 Σ g − ).