The absolute cross section for photoionization of atomic oxygen from the $2p^4{}_{}{}^3{}_{}{}^{}P$ ground state of ${\mathrm{O}}^0$ to the $2p^3{}_{}{}^4{}_{}{}^{}S$ ground state of ${\mathrm{O}}^{+}$ has been measured at five narrow wavelength intervals between 89.8 and 76.2 nm. The cross section near the $2p^3{}_{}{}^4{}_{}{}^{}S$ threshold is 4.5 Mb ± 7%. Recent calculations by Taylor and Burke, and by Pradhan and Saraph are in reasonable agreement with this work. The dipole-length results of Taylor and Burke (4.1 Mb) are in better agreement with the experiment than their dipole-velocity results (3.2 Mb).

• Received 2 November 1977

DOI:https://doi.org/10.1103/PhysRevA.18.571