Hemes, types of iron prophyrins, have been developed over many years to model aspects of ligand binding in heme proteins. Recently, the heme-ligand system has proved useful for exploring the detailed kinetics of photodissociation-geminate recombination within a solvent cage. Oxygen is a key ligand for both purposes, but most hemes are unstable in its presence. Picket fence heme is an exception, it is reasonably stable with O-2. Cage recombination efficiency in toluene solvent after photolysis with 314 nm laser light is about 43% when methylimidazole is used as the trans base, reduced to about 20% when dimethylimidazole is used to introduce trans strain. Previously, geminate rebinding of CO was unmeasurable in any model heme system, but with picket fence heme and methylimidazole, recombination efficiency appears to approach 10%, again reduced significantly by dimethylimidazole. The lifetime of the caged geminate pair is longer in the picket fence system, about 30 ps in all cases. These observations fit well with expectations from prior studies but fill some crucial gaps in the emerging picture.