Copernicium (112Cn) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 277Cn in 1996. There are seven known radioisotopes (with one more unconfirmed); the longest-lived isotope is 285Cn with a half-life of 28 seconds.
List of isotopes
Isotopes and nuclear properties
Nucleosynthesis Superheavy elements such as copernicium are produced by bombarding lighter elements in particle accelerators that induces fusion reactions. Whereas most of the isotopes of copernicium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher atomic numbers. Depending on the energies involved, the former are separated into "hot" and "cold". In hot fusion reactions, very light, high-energy projectiles are accelerated toward very heavy targets such as actinides, giving rise to compound nuclei at high excitation energy (~40–50 MeV) that may either fission or evaporate several (3 to 5) neutrons. In cold fusion reactions, the produced fused nuclei have a relatively low excitation energy (~10–20 MeV), which decreases the probability that these products will undergo fission reactions. As the fused nuclei cool to the ground state, they require emission of only one or two neutrons, and thus, allows for the generation of more neutron-rich products. The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see cold fusion). The table below contains various combinations of targets and projectiles which could be used to form compound nuclei with Z = 112.
Cold fusion The first cold fusion reaction to produce copernicium was performed by GSI in 1996, who reported the detection of two decay chains of copernicium-277.
20882Pb + 7030Zn → 277112Cn + n In a review of the data in 2000, the first decay chain was retracted. In a repeat of the reaction in 2000 they were able to synthesize a further atom. They attempted to measure the 1n excitation function in 2002 but suffered from a failure of the zinc-70 beam. The unofficial discovery of copernicium-277 was confirmed in 2004 at RIKEN, where researchers detected a further two atoms of the isotope and were able to confirm the decay data for the entire chain. This reaction had also previously been tried in 1971 at the Joint Institute for Nuclear Research in Dubna, Russia in an effort to produce 276Cn in the 2n channel, but without success. After the successful synthesis of copernicium-277, the GSI team performed a reaction using a 68Zn projectile in 1997 in an effort to study the effect of isospin (neutron richness) on the chemical yield.
20882Pb + 6830Zn → 276−x112Cn + x n The experiment was initiated after the discovery of a yield enhancement during the synthesis of darmstadtium isotopes using nickel-62 and nickel-64 ions. No decay chains of copernicium-275 were detected leading to a cross section limit of 1.2 picobarns (pb). However, the revision of the yield for the zinc-70 reaction to 0.5 pb does not rule out a similar yield for this reaction. In 1990, after some early indications for the formation of isotopes of copernicium in the irradiation of a tungsten target with multi-GeV protons, a collaboration between GSI and the Hebrew University studied the foregoing reaction.
18474W + 8838Sr → 272−x112Cn + x n They were able to detect some spontaneous fission (SF) activity and a 12.5 MeV alpha decay, both of which they tentatively assigned to the radiative capture product copernicium-272 or the 1n evaporation residue copernicium-271. Both the TWG and JWP have concluded that a lot more research is required to confirm these conclusions.
Hot fusion In 1998, the team at the Flerov Laboratory of Nuclear Research (FLNR) in Dubna, Russia began a research program using calcium-48 nuclei in "warm" fusion reactions leading to super-heavy elements. In March 1998, they claimed to have synthesized two atoms of the element in the following reaction.
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