Some O I oscillator strengths and the interstellar abundance of oxygen

The interstellar absorption line due to the O I intersystem transition $$2p^{4}\enspace ^3P_2-2p^3\enspace 3s\enspace^5S^0_2$$ at 1355.598 Å has been detected in the direction of ζ Oph with an equivalent width of 6.6 ± 0.4 (1σ)mÅ. Extensive calculations of the lifetime of the $$^5S^0$$ term have been made and the results are consistent with measurements. The value $$\textit f(\lambda \enspace 1355.6)=(12.5\pm0.18)\times10^{-6}$$ is adopted. For the other two observed lines of O I adopted values are $$\textit f(\lambda \enspace 1302.169)=0.0486$$ from lifetime experiments and $$\textit f(\lambda \enspace 1309.230)=0.0092$$ from theory. Theoretical $$\textit f$$ values are also given for other O I resonance transitions, $$2p^4\enspace ^3P-2p^3\enspace ns\enspace ^3S$$ and $$2p^3\enspace nd \enspace ^3D$$. The resulting limits on the O I column density (cm⁻²) are $$17.45\leqslant\text {log}\enspace N\leqslant17.70$$. Since log N = 21.13 for the hydrogen column density in H I regions and the solar number ratio is log (0/H) = −3.17, the interstellar gaseous oxygen is depleted by a factor between 1.8 and 3.2. Improved determinations of the abundances of P II and Ni II also are reported.