A graphic depiction of anuclear fusion reaction. Two nuclei fuse into one, emitting aneutron. Reactions that created new elements to this moment were similar, with the only possible difference that several singular neutrons sometimes were released, or none at all.
A superheavy[a]atomic nucleus is created in a nuclear reaction that combines two other nuclei of unequal size[b] into one; roughly, the more unequal the two nuclei in terms ofmass, the greater the possibility that the two react.[16] The material made of the heavier nuclei is made into a target, which is then bombarded by thebeam of lighter nuclei. Two nuclei can onlyfuse into one if they approach each other closely enough; normally, nuclei (all positively charged) repel each other due toelectrostatic repulsion. Thestrong interaction can overcome this repulsion but only within a very short distance from a nucleus; beam nuclei are thus greatlyaccelerated in order to make such repulsion insignificant compared to the velocity of the beam nucleus.[17] The energy applied to the beam nuclei to accelerate them can cause them to reach speeds as high as one-tenth of thespeed of light. However, if too much energy is applied, the beam nucleus can fall apart.[17]
Coming close enough alone is not enough for two nuclei to fuse: when two nuclei approach each other, they usually remain together for about 10−20 seconds and then part ways (not necessarily in the same composition as before the reaction) rather than form a single nucleus.[17][18] This happens because during the attempted formation of a single nucleus, electrostatic repulsion tears apart the nucleus that is being formed.[17] Each pair of a target and a beam is characterized by itscross section—the probability that fusion will occur if two nuclei approach one another expressed in terms of the transverse area that the incident particle must hit in order for the fusion to occur.[c] This fusion may occur as a result of the quantum effect in which nuclei cantunnel through electrostatic repulsion. If the two nuclei can stay close past that phase, multiple nuclear interactions result in redistribution of energy and an energy equilibrium.[17]
The resulting merger is anexcited state[21]—termed acompound nucleus—and thus it is very unstable.[17] To reach a more stable state, the temporary merger mayfission without formation of a more stable nucleus.[22] Alternatively, the compound nucleus may eject a fewneutrons, which would carry away the excitation energy; if the latter is not sufficient for a neutron expulsion, the merger would produce agamma ray. This happens in about 10−16 seconds after the initial nuclear collision and results in creation of a more stable nucleus.[22] The definition by theIUPAC/IUPAP Joint Working Party (JWP) states that achemical element can only be recognized as discovered if a nucleus of it has notdecayed within 10−14 seconds. This value was chosen as an estimate of how long it takes a nucleus to acquireelectrons and thus display its chemical properties.[23][d]
The beam passes through the target and reaches the next chamber, the separator; if a new nucleus is produced, it is carried with this beam.[25] In the separator, the newly produced nucleus is separated from other nuclides (that of the original beam and any other reaction products)[e] and transferred to asurface-barrier detector, which stops the nucleus. The exact location of the upcoming impact on the detector is marked; also marked are its energy and the time of the arrival.[25] The transfer takes about 10−6 seconds; in order to be detected, the nucleus must survive this long.[28] The nucleus is recorded again once its decay is registered, and the location, theenergy, and the time of the decay are measured.[25]
Stability of a nucleus is provided by the strong interaction. However, its range is very short; as nuclei become larger, its influence on the outermostnucleons (protons and neutrons) weakens. At the same time, the nucleus is torn apart by electrostatic repulsion between protons, and its range is not limited.[29] Totalbinding energy provided by the strong interaction increases linearly with the number of nucleons, whereas electrostatic repulsion increases with the square of the atomic number, i.e. the latter grows faster and becomes increasingly important for heavy and superheavy nuclei.[30][31] Superheavy nuclei are thus theoretically predicted[32] and have so far been observed[33] to predominantly decay via decay modes that are caused by such repulsion:alpha decay andspontaneous fission.[f] Almost all alpha emitters have over 210 nucleons,[35] and the lightest nuclide primarily undergoing spontaneous fission has 238.[36] In both decay modes, nuclei are inhibited from decaying by correspondingenergy barriers for each mode, but they can be tunneled through.[30][31]
Scheme of an apparatus for creation of superheavy elements, based on the Dubna Gas-Filled Recoil Separator set up in theFlerov Laboratory of Nuclear Reactions in JINR. The trajectory within the detector and the beam focusing apparatus changes because of adipole magnet in the former andquadrupole magnets in the latter.[37]
Alpha particles are commonly produced in radioactive decays because the mass of an alpha particle per nucleon is small enough to leave some energy for the alpha particle to be used as kinetic energy to leave the nucleus.[38] Spontaneous fission is caused by electrostatic repulsion tearing the nucleus apart and produces various nuclei in different instances of identical nuclei fissioning.[31] As the atomic number increases, spontaneous fission rapidly becomes more important: spontaneous fission partial half-lives decrease by 23 orders of magnitude fromuranium (element 92) tonobelium (element 102),[39] and by 30 orders of magnitude fromthorium (element 90) tofermium (element 100).[40] The earlierliquid drop model thus suggested that spontaneous fission would occur nearly instantly due to disappearance of thefission barrier for nuclei with about 280 nucleons.[31][41] The laternuclear shell model suggested that nuclei with about 300 nucleons would form anisland of stability in which nuclei will be more resistant to spontaneous fission and will primarily undergo alpha decay with longer half-lives.[31][41] Subsequent discoveries suggested that the predicted island might be further than originally anticipated; they also showed that nuclei intermediate between the long-lived actinides and the predicted island are deformed, and gain additional stability from shell effects.[42] Experiments on lighter superheavy nuclei,[43] as well as those closer to the expected island,[39] have shown greater than previously anticipated stability against spontaneous fission, showing the importance of shell effects on nuclei.[g]
Alpha decays are registered by the emitted alpha particles, and the decay products are easy to determine before the actual decay; if such a decay or a series of consecutive decays produces a known nucleus, the original product of a reaction can be easily determined.[h] (That all decays within a decay chain were indeed related to each other is established by the location of these decays, which must be in the same place.)[25] The known nucleus can be recognized by the specific characteristics of decay it undergoes such as decay energy (or more specifically, thekinetic energy of the emitted particle).[i] Spontaneous fission, however, produces various nuclei as products, so the original nuclide cannot be determined from its daughters.[j]
The information available to physicists aiming to synthesize a superheavy element is thus the information collected at the detectors: location, energy, and time of arrival of a particle to the detector, and those of its decay. The physicists analyze this data and seek to conclude that it was indeed caused by a new element and could not have been caused by a different nuclide than the one claimed. Often, provided data is insufficient for a conclusion that a new element was definitely created and there is no other explanation for the observed effects; errors in interpreting data have been made.[k]
The first search for element 116, using the reaction between248Cm and48Ca, was performed in 1977 by Ken Hulet and his team at theLawrence Livermore National Laboratory (LLNL). They were unable to detect any atoms of livermorium.[54]Yuri Oganessian and his team at the Flerov Laboratory of Nuclear Reactions (FLNR) in theJoint Institute for Nuclear Research (JINR) 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 calculatedcross section limit of 10–100 pb. Work on reactions with48Ca, which had proved very useful in the synthesis ofnobelium from thenatPb+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 intense48Ca 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 of48Ca with actinide targets and the discovery of the 5 heaviest elements on the periodic table:flerovium,moscovium, livermorium,tennessine, andoganesson.[55]
In late 1998, Polish physicistRobert Smolańczuk published calculations on the fusion of atomic nuclei towards the synthesis ofsuperheavy atoms, includingelements 118 and 116.[57] His calculations suggested that it might be possible to make these two elements by fusinglead withkrypton under carefully controlled conditions.[57]
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.[60] 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 authorVictor Ninov.[61][62] The isotope289Lv was finally discovered in 2024 at the JINR.[63]
Livermorium was first synthesized on July 19, 2000, when scientists atDubna (JINR) bombarded acurium-248 target with acceleratedcalcium-48 ions. A single atom was detected, decaying byalpha emission withdecay energy 10.54 MeV to an isotope offlerovium. The results were published in December 2000.[64]
Thedaughter flerovium isotope had properties matching those of a flerovium isotope first synthesized in June 1999, which was originally assigned to288Fl,[64] implying an assignment of the parent livermorium isotope to292Lv. Later work in December 2002 indicated that the synthesized flerovium isotope was actually289Fl, and hence the assignment of the synthesized livermorium atom was correspondingly altered to293Lv.[65]
Two further atoms were reported by the institute during their second experiment during April–May 2001.[66] In the same experiment they also detected a decay chain which corresponded to the first observed decay offlerovium in December 1998, which had been assigned to289Fl.[66] 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 that289Fl has different decay properties and that the first observed flerovium atom may have been itsnuclear isomer289mFl.[64][67] The observation of289mFl in this series of experiments may indicate the formation of a parent isomer of livermorium, namely293mLv, or a rare and previously unobserved decay branch of the already-discovered state293Lv to289mFl. 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 to290Fl, as the low beam energy used in that original experiment makes the 2n channel plausible; its parent could then conceivably be294Lv, but this assignment would still need confirmation in the248Cm(48Ca,2n)294Lv reaction.[64][67][68]
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-discoveredisotope as293Lv. In this run, the team also observed the isotope292Lv for the first time.[65] In further experiments from 2004 to 2006, the team replaced the curium-248 target with the lightercurium isotopecurium-245. Here evidence was found for the two isotopes290Lv and291Lv.[69]
In May 2009, theIUPAC/IUPAP Joint Working Party reported on the discovery ofcopernicium and acknowledged the discovery of the isotope283Cn.[70] This implied thede facto discovery of the isotope291Lv, from the acknowledgment of the data relating to its granddaughter283Cn, although the livermorium data was not absolutely critical for the demonstration of copernicium's discovery. Also in 2009, confirmation from Berkeley and theGesellschaft für Schwerionenforschung (GSI) 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 (not involving291Lv and283Cn) inconclusive, the results of 2004–2006 were accepted as identification of livermorium, and the element was officially recognized as having been discovered.[69]
The synthesis of livermorium has been separately confirmed at the GSI (2012) andRIKEN (2014 and 2016).[71][72] In the 2012 GSI experiment, one chain tentatively assigned to293Lv was shown to be inconsistent with previous data; it is believed that this chain may instead originate from anisomeric state,293mLv.[71] In the 2016 RIKEN experiment, one atom that may be assigned to294Lv was seemingly detected, alpha decaying to290Fl and286Cn, which underwent spontaneous fission; however, the first alpha from the livermorium nuclide produced was missed, and the assignment to294Lv is still uncertain though plausible.[73]
UsingMendeleev's nomenclature for unnamed and undiscovered elements, livermorium is sometimes calledeka-polonium.[74] In 1979 IUPAC recommended that theplaceholdersystematic element nameununhexium (Uuh)[75] 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,[76][77] who called it "element 116", with the symbol ofE116,(116), or even simply116.[1]
According to IUPAC recommendations, the discoverer or discoverers of a new element have the right to suggest a name.[78] The discovery of livermorium was recognized by the Joint Working Party (JWP) of IUPAC on 1 June 2011, along with that offlerovium.[69] According to the vice-director of JINR, the Dubna team originally wanted to name element 116moscovium, after theMoscow Oblast in which Dubna is located,[79] but it was later decided to use this name forelement 115 instead. The namelivermorium and the symbolLv were adopted on May 23,[80] 2012.[7][81] The name recognises theLawrence Livermore National Laboratory, within the city ofLivermore, California, US, which collaborated with JINR on the discovery. The city in turn is named after the American rancherRobert Livermore, a naturalized Mexican citizen of English birth.[7] The naming ceremony for flerovium and livermorium was held in Moscow on October 24, 2012.[82]
The synthesis of livermorium in fusion reactions using projectiles heavier than48Ca has been explored in preparation for synthesis attempts of the yet-undiscoveredelement 120, as such reactions would necessarily utilize heavier projectiles. In 2023, the reaction between238U and54Cr was studied at the JINR's Superheavy Element Factory in Dubna; one atom of the new isotope288Lv was reported.[83] More detailed analysis of this reaction was published in 2025, by which time another atom had been reported.[84] Similarly, in 2024, a team at theLawrence Berkeley National Laboratory reported the synthesis of two atoms of290Lv in the reaction between244Pu and50Ti. This result was described as "truly groundbreaking" byRIKEN director Hiromitsu Haba, whose team plans to search forelement 119.[85][86][87] The team at JINR studied the reaction between242Pu and50Ti in 2024 as a follow-up to the238U+54Cr, obtaining additional decay data for288Lv and its decay products (two new chains) and discovering the new isotope289Lv (three chains).[63][84]
Other than nuclear properties, no properties of livermorium or its compounds have been measured; this is due to its extremely limited and expensive production[88] and the fact that it decays very quickly. Properties of livermorium remain unknown and only predictions are available.
The expected location of the island of stability is marked by the white circle. The dotted line is the line ofbeta stability.
Livermorium is expected to be near anisland of stability centered oncopernicium (element 112) andflerovium (element 114).[89][90] Due to the expected highfission barriers, any nucleus within this island of stability exclusively decays by alpha decay and perhaps some electron capture andbeta decay.[3] While the known isotopes of livermorium do not actually have enough neutrons to be on the island of stability, they can be seen to approach the island, as the heavier isotopes are generally the longer-lived ones.[64][69]
Superheavy elements are produced bynuclear fusion. These fusion reactions can be divided into "hot" and "cold" fusion,[l] depending on the excitation energy of the compound nucleus produced. In hot fusion reactions, very light, high-energy projectiles are accelerated toward very heavy targets (actinides), giving rise to compound nuclei at high excitation energy (~40–50 MeV) that may either fission or evaporate several (3 to 5) neutrons.[92] In cold fusion reactions (which use heavier projectiles, typically from thefourth period, and lighter targets, usuallylead andbismuth), 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 theground state, they require emission of only one or two neutrons. Hot fusion reactions tend to produce more neutron-rich products because the actinides have the highest neutron-to-proton ratios of any elements that can presently be made in macroscopic quantities.[93]
Important information could be gained regarding the properties of superheavy nuclei by the synthesis of more livermorium isotopes, specifically those with a few neutrons more or less than the known ones –286Lv,287Lv,294Lv, and295Lv. This is possible because there are many reasonably long-livedisotopes of curium that can be used to make a target.[89] The light isotopes can be made by fusingcurium-243 with calcium-48. They would undergo a chain of alpha decays, ending attransactinide isotopes that are too light to achieve by hot fusion and too heavy to be produced by cold fusion.[89] The same neutron-deficient isotopes are also reachable in reactions with projectiles heavier than48Ca, which will be necessary to reach elements beyond atomic number 118 (or possibly119); this is how288Lv and289Lv were discovered.[63][83]
The synthesis of the heavy isotopes294Lv and295Lv could be accomplished by fusing the heavy curium isotopecurium-250 with calcium-48. Thecross section of this nuclear reaction would be about 1 picobarn, though it is not yet possible to produce250Cm in the quantities needed for target manufacture.[89] Alternatively,294Lv could be produced via charged-particle evaporation in the251Cf(48Ca,pn) reaction.[94][95] After a few alpha decays, these livermorium isotopes would reach nuclides at theline of beta stability. Additionally,electron capture may also become an important decay mode in this region, allowing affected nuclei to reach the middle of the island. For example, it is predicted that295Lv would alpha decay to291Fl, which would undergo successive electron capture to291Nh and then291Cn which is expected to be in the middle of the island of stability and have a half-life of about 1200 years, affording the most likely hope of reaching the middle of the island using current technology. A drawback is that the decay properties of superheavy nuclei this close to the line of beta stability are largely unexplored.[89]
Other possibilities to synthesize nuclei on the island of stability include quasifission (partial fusion followed by fission) of a massive nucleus.[96] Such nuclei tend to fission, expelling doublymagic or nearly doubly magic fragments such ascalcium-40,tin-132,lead-208, orbismuth-209.[97] Recently it has been shown that the multi-nucleon transfer reactions in collisions of actinide nuclei (such asuranium andcurium) might be used to synthesize the neutron-rich superheavy nuclei located at the island of stability,[96] although formation of the lighter elementsnobelium orseaborgium is more favored.[89] One last possibility to synthesize isotopes near the island is to use controllednuclear explosions to create aneutron flux high enough to bypass the gaps of instability at258–260Fm and atmass number 275 (atomic numbers104 to108), mimicking ther-process in which theactinides were first produced in nature and the gap of instability aroundradon bypassed.[89] Some such isotopes (especially291Cn and293Cn) may even have been synthesized in nature, but would have decayed away far too quickly (with half-lives of only thousands of years) and be produced in far too small quantities (about 10−12 the abundance oflead) to be detectable asprimordial nuclides today outsidecosmic rays.[89]
In theperiodic table, livermorium is a member of group 16, the chalcogens. It appears belowoxygen,sulfur,selenium,tellurium, and polonium. Every previous chalcogen has six electrons in its valence shell, forming avalence electron configuration of ns2np4. In livermorium's case, the trend should be continued and the valence electron configuration is predicted to be 7s27p4;[1] therefore, livermorium will have some similarities to its lightercongeners. Differences are likely to arise; a large contributing effect is thespin–orbit (SO) interaction—the mutual interaction between the electrons' motion andspin. It is especially strong for the superheavy elements, because their electrons move much faster than in lighter atoms, at velocities comparable to thespeed of light.[98] In relation to livermorium atoms, it lowers the 7s and the 7p electron energy levels (stabilizing the corresponding electrons), but two of the 7p electron energy levels are stabilized more than the other four.[99] The stabilization of the 7s electrons is called theinert pair effect, and the effect "tearing" the 7p subshell into the more stabilized and the less stabilized parts is called subshell splitting. Computation chemists see the split as a change of the second (azimuthal)quantum numberl from 1 to1⁄2 and3⁄2 for the more stabilized and less stabilized parts of the 7p subshell, respectively: the 7p1/2 subshell acts as a second inert pair, though not as inert as the 7s electrons, while the 7p3/2 subshell can easily participate in chemistry.[1][98][m] For many theoretical purposes, the valence electron configuration may be represented to reflect the 7p subshell split as 7s2 7p2 1/27p2 3/2.[1]
Inert pair effects in livermorium should be even stronger than in polonium and hence the +2oxidation state becomes more stable than the +4 state, which would be stabilized only by the mostelectronegativeligands; this is reflected in the expectedionization energies of livermorium, where there are large gaps between the second and third ionization energies (corresponding to the breaching of the unreactive 7p1/2 shell) and fourth and fifth ionization energies.[3] Indeed, the 7s electrons are expected to be so inert that the +6 state will not be attainable.[1] Themelting andboiling points of livermorium are expected to continue the trends down the chalcogens; thus livermorium should melt at a higher temperature than polonium, but boil at a lower temperature.[2] It should also bedenser than polonium (α-Lv: 12.9 g/cm3; α-Po: 9.2 g/cm3); like polonium it should also form an α and a β allotrope.[3][100] The electron of ahydrogen-like livermorium atom (oxidized so that it only has one electron, Lv115+) is expected to move so fast that it has a mass 1.86 times that of a stationary electron, due torelativistic effects. For comparison, the figures for hydrogen-like polonium and tellurium are expected to be 1.26 and 1.080 respectively.[98]
Livermorium is projected to be the fourth member of the 7p series ofchemical elements and the heaviest member of group 16 in the periodic table, belowpolonium. While it is the least theoretically studied of the 7p elements, its chemistry is expected to be quite similar to that of polonium.[3] The group oxidation state of +6 is known for all the chalcogens apart from oxygen which cannotexpand its octet and is one of the strongestoxidizing agents among the chemical elements. Oxygen is thus limited to a maximum +2 state, exhibited in the fluorideOF2. The +4 state is known forsulfur,selenium,tellurium, and polonium, undergoing a shift in stability from reducing for sulfur(IV) and selenium(IV) through being the most stable state for tellurium(IV) to being oxidizing in polonium(IV). This suggests a decreasing stability for the higher oxidation states as the group is descended due to the increasing importance of relativistic effects, especially the inert pair effect.[98] The most stable oxidation state of livermorium should thus be +2, with a rather unstable +4 state. The +2 state should be about as easy to form as it is forberyllium andmagnesium, and the +4 state should only be achieved with strongly electronegative ligands, such as in livermorium(IV) fluoride (LvF4).[1] The +6 state should not exist at all due to the very strong stabilization of the 7s electrons, making the valence core of livermorium only four electrons.[3] The lighter chalcogens are also known to form a −2 state asoxide,sulfide,selenide,telluride, andpolonide; due to the destabilization of livermorium's 7p3/2 subshell, the −2 state should be very unstable for livermorium, whose chemistry should be essentially purely cationic,[1] though the larger subshell and spinor energy splittings of livermorium as compared to polonium should make Lv2− slightly less unstable than expected.[98]
Livermorium hydride (LvH2) would be the heaviestchalcogen hydride and the heaviest homologue ofwater (the lighter ones areH2S,H2Se,H2Te, andPoH2). Polane (polonium hydride) is a morecovalent compound than most metal hydrides because polonium straddles the border betweenmetal andmetalloid and has some nonmetallic properties: it is intermediate between ahydrogen halide likehydrogen chloride (HCl) and ametal hydride likestannane (SnH4). Livermorane should continue this trend: it should be a hydride rather than a livermoride, but still a covalentmolecular compound. Spin-orbit interactions are expected to make the Lv–H bond longer than expected fromperiodic trends alone, and make the H–Lv–H bond angle larger than expected: this is theorized to be because the unoccupied 8s orbitals are relatively low in energy and canhybridize with the valence 7p orbitals of livermorium. This phenomenon, dubbed "supervalent hybridization",[101] has some analogues in non-relativistic regions in the periodic table; for example, molecularcalcium difluoride has 4s and 3d involvement from thecalcium atom.[102] The heavier livermorium dihalides are predicted to belinear, but the lighter ones are predicted to bebent.[103]
Unambiguous determination of the chemical characteristics of livermorium has not yet been established.[104][105] In 2011, experiments were conducted to createnihonium,flerovium, andmoscovium isotopes in the reactions between calcium-48 projectiles and targets of americium-243 andplutonium-244. The targets includedlead andbismuth impurities and hence some isotopes of bismuth andpolonium were generated in nucleon transfer reactions. This, while an unforeseen complication, could give information that would help in the future chemical investigation of the heavier homologs of bismuth and polonium, which are respectively moscovium and livermorium.[105] The produced nuclidesbismuth-213 andpolonium-212m were transported as the hydrides213BiH3 and212mPoH2 at 850 °C through a quartz wool filter unit held withtantalum, showing that these hydrides were surprisingly thermally stable, although their heavier congeners McH3 and LvH2 would be expected to be less thermally stable from simple extrapolation ofperiodic trends in the p-block.[105] Further calculations on the stability and electronic structure of BiH3, McH3, PoH2, and LvH2 are needed before chemical investigations take place. Moscovium and livermorium are expected to bevolatile enough as pure elements for them to be chemically investigated in the near future, a property livermorium would then share with its lighter congener polonium, though the short half-lives of all presently known livermorium isotopes means that the element is still inaccessible to experimental chemistry.[105][106]
^Innuclear physics, an element is calledheavy if its atomic number is high;lead (element 82) is one example of such a heavy element. The term "superheavy elements" typically refers to elements with atomic number greater than103 (although there are other definitions, such as atomic number greater than100[11] or112;[12] sometimes, the term is presented an equivalent to the term "transactinide", which puts an upper limit before the beginning of the hypotheticalsuperactinide series).[13] Terms "heavy isotopes" (of a given element) and "heavy nuclei" mean what could be understood in the common language—isotopes of high mass (for the given element) and nuclei of high mass, respectively.
^In 2009, a team at the JINR led by Oganessian published results of their attempt to create hassium in a symmetric136Xe + 136Xe reaction. They failed to observe a single atom in such a reaction, putting the upper limit on the cross section, the measure of probability of a nuclear reaction, as 2.5 pb.[14] In comparison, the reaction that resulted in hassium discovery,208Pb +58Fe, had a cross section of ~20 pb (more specifically, 19+19 -11 pb), as estimated by the discoverers.[15]
^The amount of energy applied to the beam particle to accelerate it can also influence the value of cross section. For example, in the28 14Si +1 0n →28 13Al +1 1p reaction, cross section changes smoothly from 370 mb at 12.3 MeV to 160 mb at 18.3 MeV, with a broad peak at 13.5 MeV with the maximum value of 380 mb.[19]
^This figure also marks the generally accepted upper limit for lifetime of a compound nucleus.[24]
^This separation is based on that the resulting nuclei move past the target more slowly then the unreacted beam nuclei. The separator contains electric and magnetic fields whose effects on a moving particle cancel out for a specific velocity of a particle.[26] Such separation can also be aided by atime-of-flight measurement and a recoil energy measurement; a combination of the two may allow to estimate the mass of a nucleus.[27]
^It was already known by the 1960s that ground states of nuclei differed in energy and shape as well as that certain magic numbers of nucleons corresponded to greater stability of a nucleus. However, it was assumed that there was no nuclear structure in superheavy nuclei as they were too deformed to form one.[39]
^Since mass of a nucleus is not measured directly but is rather calculated from that of another nucleus, such measurement is called indirect. Direct measurements are also possible, but for the most part they have remained unavailable for superheavy nuclei.[44] The first direct measurement of mass of a superheavy nucleus was reported in 2018 at LBNL.[45] Mass was determined from the location of a nucleus after the transfer (the location helps determine its trajectory, which is linked to the mass-to-charge ratio of the nucleus, since the transfer was done in presence of a magnet).[46]
^If the decay occurred in a vacuum, then since total momentum of an isolated system before and after the decaymust be preserved, the daughter nucleus would also receive a small velocity. The ratio of the two velocities, and accordingly the ratio of the kinetic energies, would thus be inverse to the ratio of the two masses. The decay energy equals the sum of the known kinetic energy of the alpha particle and that of the daughter nucleus (an exact fraction of the former).[35] The calculations hold for an experiment as well, but the difference is that the nucleus does not move after the decay because it is tied to the detector.
^Spontaneous fission was discovered by Soviet physicistGeorgy Flerov,[47] a leading scientist at JINR, and thus it was a "hobbyhorse" for the facility.[48] In contrast, the LBL scientists believed fission information was not sufficient for a claim of synthesis of an element. They believed spontaneous fission had not been studied enough to use it for identification of a new element, since there was a difficulty of establishing that a compound nucleus had only ejected neutrons and not charged particles like protons or alpha particles.[24] They thus preferred to link new isotopes to the already known ones by successive alpha decays.[47]
^For instance, element 102 was mistakenly identified in 1957 at the Nobel Institute of Physics inStockholm,Stockholm County,Sweden.[49] There were no earlier definitive claims of creation of this element, and the element was assigned a name by its Swedish, American, and British discoverers,nobelium. It was later shown that the identification was incorrect.[50] The following year, RL was unable to reproduce the Swedish results and announced instead their synthesis of the element; that claim was also disproved later.[50] JINR insisted that they were the first to create the element and suggested a name of their own for the new element,joliotium;[51] the Soviet name was also not accepted (JINR later referred to the naming of the element 102 as "hasty").[52] This name was proposed to IUPAC in a written response to their ruling on priority of discovery claims of elements, signed 29 September 1992.[52] The name "nobelium" remained unchanged on account of its widespread usage.[53]
^Despite the name, "cold fusion" in the context of superheavy element synthesis is a distinct concept from the idea that nuclear fusion can be achieved in room temperature conditions (seecold fusion).[91]
^The quantum number corresponds to the letter in the electron orbital name: 0 to s, 1 to p, 2 to d, etc. Seeazimuthal quantum number for more information.
^abcdefghijHoffman, Darleane C.; Lee, Diana M.; Pershina, Valeria (2006). "Transactinides and the future elements". In Morss; Edelstein, Norman M.; Fuger, Jean (eds.).The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Dordrecht, The Netherlands:Springer Science+Business Media.ISBN978-1-4020-3555-5.
^Thayer, John S. (2010). "Relativistic Effects and the Chemistry of the Heavier Main Group Elements".Relativistic Methods for Chemists. Challenges and Advances in Computational Chemistry and Physics. Vol. 10. p. 83.doi:10.1007/978-1-4020-9975-5_2.ISBN978-1-4020-9974-8.
^Pershina, Valeria. "Theoretical Chemistry of the Heaviest Elements". In Schädel, Matthias; Shaughnessy, Dawn (eds.).The Chemistry of Superheavy Elements (2nd ed.). Springer Science & Business Media. p. 154.ISBN9783642374661.
^"Популярная библиотека химических элементов. Сиборгий (экавольфрам)" [Popular library of chemical elements. Seaborgium (eka-tungsten)].n-t.ru (in Russian). Retrieved2020-01-07. Reprinted from"Экавольфрам" [Eka-tungsten].Популярная библиотека химических элементов. Серебро – Нильсборий и далее [Popular library of chemical elements. Silver through nielsbohrium and beyond] (in Russian).Nauka. 1977.
^Hofmann, S.; Heinz, S.; Mann, R.; Maurer, J.; Münzenberg, G.; Antalic, S.; Barth, W.; Burkhard, H. G.; Dahl, L.; Eberhardt, K.; Grzywacz, R.; Hamilton, J. H.; Henderson, R. A.; Kenneally, J. M.; Kindler, B.; Kojouharov, I.; Lang, R.; Lommel, B.; Miernik, K.; Miller, D.; Moody, K. J.; Morita, K.; Nishio, K.; Popeko, A. G.; Roberto, J. B.; Runke, J.; Rykaczewski, K. P.; Saro, S.; Scheidenberger, C.; Schött, H. J.; Shaughnessy, D. A.; Stoyer, M. A.; Thörle-Popiesch, P.; Tinschert, K.; Trautmann, N.; Uusitalo, J.; Yeremin, A. V. (2016)."Review of even element super-heavy nuclei and search for element 120".The European Physical Journal A.2016 (52): 180.Bibcode:2016EPJA...52..180H.doi:10.1140/epja/i2016-16180-4.OSTI1410078.S2CID124362890.
^abHofmann, S.; Heinz, S.; Mann, R.; Maurer, J.; Khuyagbaatar, J.; Ackermann, D.; Antalic, S.; Barth, W.; Block, M.; Burkhard, H. G.; Comas, V. F.; Dahl, L.; Eberhardt, K.; Gostic, J.; Henderson, R. A.; Heredia, J. A.; Heßberger, F. P.; Kenneally, J. M.; Kindler, B.; Kojouharov, I.; Kratz, J. V.; Lang, R.; Leino, M.; Lommel, B.; Moody, K. J.; Münzenberg, G.; Nelson, S. L.; Nishio, K.; Popeko, A. G.; et al. (2012). "The reaction48Ca +248Cm →296116* studied at the GSI-SHIP".The European Physical Journal A.48 (5): 62.Bibcode:2012EPJA...48...62H.doi:10.1140/epja/i2012-12062-1.S2CID121930293.
^ab"В ЛЯР ОИЯИ впервые в мире синтезирован ливерморий-288" [Livermorium-288 was synthesized for the first time in the world at FLNR JINR] (in Russian). Joint Institute for Nuclear Research. 23 October 2023. Retrieved18 November 2023.
^abOganessian, Yu. Ts.; Utyonkov, V. K.; Abdullin, F. Sh.; Dmitriev, S. N.; Ibadullayev, D.; Itkis, M. G.; Karpov, A. V.; Kovrizhnykh, N. D.; Kuznetsov, D. A.; Petrushkin, O. V.; Podshibiakin, A. V.; Polyakov, A. N.; Popeko, A. G.; Sagaidak, R. N.; Saiko, V. V.; Schlattauer, L.; Shubin, V. D.; Shumeiko, M. V.; Solovyev, D. I.; Tsyganov, Yu. S.; Voinov, A. A.; Subbotin, V. G.; Sabelnikov, A. V.; Abdusamadzoda, D.; Bodrov, A. Yu.; Voronyuk, M. G.; Bozhikov, G. A.; Aksenov, N. V.; Khalkin, A. V.; Gan, Z. G.; Zhang, Z. Y.; Huang, M. H.; Yang, H. B.; Wang, J. G.; Zhang, M. M.; Huang, X. Y. (2025). "Investigation of reactions with50Ti and54Cr for the synthesis of new elements".Physical Review C.112: 014603.doi:10.1103/k2g4-5k7x.
^Gates, J. M.; Orford, R.; Rudolph, D.; Appleton, C.; Barrios, B. M.; Benitez, J. Y.; Bordeau, M.; Botha, W.; Campbell, C. M. (2024-07-22). "Towards the Discovery of New Elements: Production of Livermorium (Z=116) with50Ti".arXiv:2407.16079 [nucl-ex].
^Considine, Glenn D.; Kulik, Peter H. (2002).Van Nostrand's scientific encyclopedia (9th ed.). Wiley-Interscience.ISBN978-0-471-33230-5.OCLC223349096.
^Fleischmann, Martin; Pons, Stanley (1989). "Electrochemically induced nuclear fusion of deuterium".Journal of Electroanalytical Chemistry and Interfacial Electrochemistry.261 (2):301–308.doi:10.1016/0022-0728(89)80006-3.
^Armbruster, Peter & Münzenberg, Gottfried (1989). "Creating superheavy elements".Scientific American.34:36–42.
^Hong, J.; Adamian, G. G.; Antonenko, N. V.; Jachimowicz, P.; Kowal, M. (26 April 2023).Interesting fusion reactions in superheavy region(PDF). IUPAP Conference "Heaviest nuclei and atoms". Joint Institute for Nuclear Research. Retrieved30 July 2023.
^abcdeThayer, John S. (2010). "Relativistic Effects and the Chemistry of the Heavier Main Group Elements".Relativistic Methods for Chemists. Challenges and Advances in Computational Chemistry and Physics. Vol. 10. p. 83.doi:10.1007/978-1-4020-9975-5_2.ISBN978-1-4020-9974-8.
^Van WüLlen, C.; Langermann, N. (2007). "Gradients for two-component quasirelativistic methods. Application to dihalogenides of element 116".The Journal of Chemical Physics.126 (11): 114106.Bibcode:2007JChPh.126k4106V.doi:10.1063/1.2711197.PMID17381195.
^Düllmann, Christoph E. (2012). "Superheavy elements at GSI: a broad research program with element 114 in the focus of physics and chemistry".Radiochimica Acta.100 (2):67–74.doi:10.1524/ract.2011.1842.S2CID100778491.
^Moody, Ken (2013-11-30). "Synthesis of Superheavy Elements". In Schädel, Matthias; Shaughnessy, Dawn (eds.).The Chemistry of Superheavy Elements (2nd ed.). Springer Science & Business Media. pp. 24–8.ISBN978-3-642-37466-1.
