A time history diagnostic plot showing the evolution of oxygen states (top panel) for the photo-ionisation non-equilibrium (PINe isobaric) case starting at T=106 at t=0 for nH=10-4 cm-3, solar enriched gas under a z=1 Haardt & Madau (2001) background. The middle panel shows timescales including the recombination timescales of various oxygen ions (in colour), the cooling timescale, and the dynamical timescale. The bottom shows the temperature history. Recombination timescales become significant compared to the cooling timescale, creating recombination lags and delaying cooling during the peak of the cooling curve. This figure is meant to be compared and contrasted with the adjacent four figures here on the website. Note the cooling time is effectively infinite after 800 Myr, but jumps around due to small inaccuracies of our method at the equilibrium temperature.