Photoionization and Total Absorption Cross Section of Gases. II. O2 and N2 in the Region 850–1500 A

Abstract

Absorption and photo‐ionization cross sections of O₂ were measured at a number of wavelengths primarily in the region 850–1100 A by a photoelectric method. The Rydberg bands H, H′, M and M′ were found to be strongly pre‐ionized, and vibrational structures in the underlying continuum appeared to be present. The photoionization method gave 12.08±0.01 ev as the first ionization potential of O₂. This value, combined with data from emission spectra, yielded a value 6.65 ev for the dissociation energy of O₂⁺ and 16.83 ev for the third ionization potential of O₂ (O₂⁺A²Π_u←O₂X ³Σ_g^‐). In the case of N₂, a number of ``windows'' were observed and it was not possible to establish the presence of an absorption continuum in the region 850–1100 A.