Californium a nuclear explosion. Californium is not a major radionuclide at United States Department of Energy legacy sites since it was not produced in large quantities. Californium was once believed to be produced in supernovas, as their decay matches the 60-day half-life of Cf. However, subsequent studies failed to demonstrate any californium spectra, and supernova light curves are now thought to follow the decay of nickel-56. The transuranic elements from americium to fermium, including californium, occurred naturally in the natural nuclear fission reactor at Oklo, but no longer do so. Californium is produced in nuclear reactors and particle accelerators. Californium-250 is
Californium compounds +3 oxidation states include the sulfide and metallocene. Californium(IV) oxide (black brown, CfO), californium(IV) fluoride (green, CfF) represent the IV oxidation state. The II state is represented by californium(II) bromide (yellow, CfBr) and californium(II) iodide (dark violet, CfI). Californium(IV) oxide (CfO) is a black-brown solid that has a cubic crystal structure with a lattice parameter, the distance between unit cells in the crystal, of 531.0 ± 0.2 pm. Crystals of californium(III) oxide normally have a body-centered cubic symmetry. They convert to a monoclinic form upon heating to about 1400 °C and melt at 1750 °C. Californium(III) chloride (CfCl) is an