Isotopes of californium Isotopes of californium Californium (Cf) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was Cf in 1950. There are 20 known radioisotopes ranging from Cf to Cf and one nuclear isomer, Cf. The longest-lived isotope is Cf with a half-life of 900 years. Californium-252 (Cf-252) undergoes spontaneous fission and is used in small sized neutron sources. Fission neutrons have an energy range of 0 to 13 MeV with a mean value of 2.3 MeV and a most probable value of
Californium made by bombarding berkelium-249 () with neutrons, forming berkelium-250 () via neutron capture (n,γ) which, in turn, quickly beta decays (β) to californium-250 () in the following reaction: Bombardment of californium-250 with neutrons produces californium-251 and californium-252. Prolonged irradiation of americium, curium, and plutonium with neutrons produces milligram amounts of californium-252 and microgram amounts of californium-249. As of 2006, curium isotopes 244 to 248 are irradiated by neutrons in special reactors to produce primarily californium-252 with lesser amounts of isotopes 249 to 255. Microgram quantities of californium-252 are available for commercial use through the U.S. Nuclear Regulatory Commission. Only two