Livermorium
Livermorium is a synthetic chemical element; it has symbol Lv and atomic number 116. It is an extremely radioactive element that has only been created in a laboratory setting and has not been observed in nature. The element is named after the Lawrence Livermore National Laboratory in the United States, which collaborated with the Joint Institute for Nuclear Research in Dubna, Russia, to discover livermorium during experiments conducted between 2000 and 2006. The name of the laboratory refers to the city of Livermore, California, where it is located, which in turn was named after the rancher and landowner Robert Livermore. The name was adopted by IUPAC on May 30, 2012. Six isotopes of livermorium are known, with mass numbers of 288–293 inclusive; the longest-lived among them is livermorium-293 with a half-life of about 80 milliseconds. A seventh possible isotope with mass number 294 has been reported but not yet confirmed.
In the periodic table, it is a p-block transactinide element. It is a member of the 7th period and is placed in group 16 as the heaviest chalcogen, but it has not been confirmed to behave as the heavier homologue to the chalcogen polonium. Livermorium is calculated to have some similar properties to its lighter homologues, and be a post-transition metal, though it should also show several major differences from them.
Introduction
History
Unsuccessful synthesis attempts
The first search for element 116, using the reaction between 248Cm and 48Ca, was performed in 1977 by Ken Hulet and his team at the Lawrence Livermore National Laboratory. They were unable to detect any atoms of livermorium. Yuri Oganessian and his team at the Flerov Laboratory of Nuclear Reactions in the Joint Institute for Nuclear Research subsequently attempted the reaction in 1978 and met failure. In 1985, in a joint experiment between Berkeley and Peter Armbruster's team at GSI, the result was again negative, with a calculated cross section limit of 10–100 pb. Work on reactions with 48Ca, which had proved very useful in the synthesis of nobelium from the natPb+48Ca reaction, nevertheless continued at Dubna, with a superheavy element separator being developed in 1989, a search for target materials and starting of collaborations with LLNL being started in 1990, production of more intense 48Ca beams being started in 1996, and preparations for long-term experiments with 3 orders of magnitude higher sensitivity being performed in the early 1990s. This work led directly to the production of new isotopes of elements 112 to 118 in the reactions of 48Ca with actinide targets and the discovery of the 5 heaviest elements on the periodic table: flerovium, moscovium, livermorium, tennessine, and oganesson.In 1995, an international team led by Sigurd Hofmann at the Gesellschaft für Schwerionenforschung in Darmstadt, Germany attempted to synthesise element 116 in a radiative capture reaction between a lead-208 target and selenium-82 projectiles. No atoms of element 116 were identified.
Unconfirmed discovery claims
In late 1998, Polish physicist Robert Smolańczuk published calculations on the fusion of atomic nuclei towards the synthesis of superheavy atoms, including elements 118 and 116. His calculations suggested that it might be possible to make these two elements by fusing lead with krypton under carefully controlled conditions.In 1999, researchers at Lawrence Berkeley National Laboratory made use of these predictions and announced the discovery of elements 118 and 116, in a paper published in Physical Review Letters, and very soon after the results were reported in Science. The researchers reported to have performed the reaction
The following year, they published a retraction after researchers at other laboratories were unable to duplicate the results and the Berkeley lab itself was unable to duplicate them as well. In June 2002, the director of the lab announced that the original claim of the discovery of these two elements had been based on data fabricated by principal author Victor Ninov. The isotope 289Lv was finally discovered in 2024 at the JINR.
Discovery
Livermorium was first synthesized on July 19, 2000, when scientists at Dubna bombarded a curium-248 target with accelerated calcium-48 ions. A single atom was detected, decaying by alpha emission with decay energy 10.54 MeV to an isotope of flerovium. The results were published in December 2000.The daughter flerovium isotope had properties matching those of a flerovium isotope first synthesized in June 1999, which was originally assigned to 288Fl, implying an assignment of the parent livermorium isotope to 292Lv. Later work in December 2002 indicated that the synthesized flerovium isotope was actually 289Fl, and hence the assignment of the synthesized livermorium atom was correspondingly altered to 293Lv.
Road to confirmation
Two further atoms were reported by the institute during their second experiment during April–May 2001. In the same experiment they also detected a decay chain which corresponded to the first observed decay of flerovium in December 1998, which had been assigned to 289Fl. No flerovium isotope with the same properties as the one found in December 1998 has ever been observed again, even in repeats of the same reaction. Later it was found that 289Fl has different decay properties and that the first observed flerovium atom may have been its nuclear isomer 289mFl. The observation of 289mFl in this series of experiments may indicate the formation of a parent isomer of livermorium, namely 293mLv, or a rare and previously unobserved decay branch of the already-discovered state 293Lv to 289mFl. Neither possibility is certain, and research is required to positively assign this activity. Another possibility suggested is the assignment of the original December 1998 atom to 290Fl, as the low beam energy used in that original experiment makes the 2n channel plausible; its parent could then conceivably be 294Lv, but this assignment would still need confirmation in the 248Cm294Lv reaction.The team repeated the experiment in April–May 2005 and detected 8 atoms of livermorium. The measured decay data confirmed the assignment of the first-discovered isotope as 293Lv. In this run, the team also observed the isotope 292Lv for the first time. In further experiments from 2004 to 2006, the team replaced the curium-248 target with the lighter curium isotope curium-245. Here evidence was found for the two isotopes 290Lv and 291Lv.
In May 2009, the IUPAC/IUPAP Joint Working Party reported on the discovery of copernicium and acknowledged the discovery of the isotope 283Cn. This implied the de facto discovery of the isotope 291Lv, from the acknowledgment of the data relating to its granddaughter 283Cn, although the livermorium data was not absolutely critical for the demonstration of copernicium's discovery. Also in 2009, confirmation from Berkeley and the Gesellschaft für Schwerionenforschung in Germany came for the flerovium isotopes 286 to 289, immediate daughters of the four known livermorium isotopes. In 2011, IUPAC evaluated the Dubna team experiments of 2000–2006. Whereas they found the earliest data inconclusive, the results of 2004–2006 were accepted as identification of livermorium, and the element was officially recognized as having been discovered.
The synthesis of livermorium has been separately confirmed at the GSI and RIKEN. In the 2012 GSI experiment, one chain tentatively assigned to 293Lv was shown to be inconsistent with previous data; it is believed that this chain may instead originate from an isomeric state, 293mLv. In the 2016 RIKEN experiment, one atom that may be assigned to 294Lv was seemingly detected, alpha decaying to 290Fl and 286Cn, which underwent spontaneous fission; however, the first alpha from the livermorium nuclide produced was missed, and the assignment to 294Lv is still uncertain though plausible.
Naming
Using Mendeleev's nomenclature for unnamed and undiscovered elements, livermorium is sometimes called eka-polonium. In 1979 IUPAC recommended that the placeholder systematic element name ununhexium be used until the discovery of the element was confirmed and a name was decided. Although widely used in the chemical community on all levels, from chemistry classrooms to advanced textbooks, the recommendations were mostly ignored among scientists in the field, who called it "element 116", with the symbol of E116, , or even simply 116.According to IUPAC recommendations, the discoverer or discoverers of a new element have the right to suggest a name. The discovery of livermorium was recognized by the Joint Working Party of IUPAC on 1 June 2011, along with that of flerovium. According to the vice-director of JINR, the Dubna team originally wanted to name element 116 moscovium, after the Moscow Oblast in which Dubna is located, but it was later decided to use this name for element 115 instead. The name livermorium and the symbol Lv were adopted on May 23, 2012. The name recognises the Lawrence Livermore National Laboratory, within the city of Livermore, California, US, which collaborated with JINR on the discovery. The city in turn is named after the American rancher Robert Livermore, a naturalized Mexican citizen of English birth. The naming ceremony for flerovium and livermorium was held in Moscow on October 24, 2012.