K-shell Emission from O VI Near 19 Å

Laboratory measurements of O VI K-shell emission lines are presented that are situated near the O VIII Lyα line at 19 Å. The data provide additional rest-frame references for velocity determinations based on absorption features in the spectra of warm absorbers in active galactic nuclei and other astrophysical objects. They also provide benchmarks for testing atomic structure calculations of energy levels with electrons in a high principal quantum number (n = 3, 4). Excellent agreement is found with our calculations using the many-body perturbation theory method, and we provide a complete listing of the O VI energy levels calculated with this approach.