Moscovium is an extremelyradioactive element: its most stable knownisotope, moscovium-290, has ahalf-life of only 0.65 seconds.[8] In theperiodic table, it is ap-blocktransactinide element. It is a member of the7th period and is placed in group 15 as the heaviestpnictogen. Moscovium is calculated to have some properties similar to its lighter homologues,nitrogen,phosphorus,arsenic,antimony, andbismuth, and to be apost-transition metal, although it should also show several major differences from them. In particular, moscovium should also have significant similarities tothallium, as both have one rather loosely bound electron outside a quasi-closedshell. Chemical experimentation on single atoms has confirmed theoretical expectations that moscovium is less reactive than its lighter homologue bismuth. Over a hundred atoms of moscovium have been observed to date, all of which have been shown to have mass numbers from 286 to 290.
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.[17] 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.[18] 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.[18]
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.[18][19] This happens because during the attempted formation of a single nucleus, electrostatic repulsion tears apart the nucleus that is being formed.[18] 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.[18]
The resulting merger is anexcited state[22]—termed acompound nucleus—and thus it is very unstable.[18] To reach a more stable state, the temporary merger mayfission without formation of a more stable nucleus.[23] 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.[23] 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.[24][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.[26] 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.[26] The transfer takes about 10−6 seconds; in order to be detected, the nucleus must survive this long.[29] The nucleus is recorded again once its decay is registered, and the location, theenergy, and the time of the decay are measured.[26]
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.[30] 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.[31][32] Superheavy nuclei are thus theoretically predicted[33] and have so far been observed[34] 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,[36] and the lightest nuclide primarily undergoing spontaneous fission has 238.[37] In both decay modes, nuclei are inhibited from decaying by correspondingenergy barriers for each mode, but they can be tunneled through.[31][32]
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.[38]
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.[39] Spontaneous fission is caused by electrostatic repulsion tearing the nucleus apart and produces various nuclei in different instances of identical nuclei fissioning.[32] 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),[40] and by 30 orders of magnitude fromthorium (element 90) tofermium (element 100).[41] 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.[32][42] 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.[32][42] 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.[43] Experiments on lighter superheavy nuclei,[44] as well as those closer to the expected island,[40] 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.)[26] 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]
A view of the famousRed Square inMoscow. The region around the city was honored by the discoverers as "the ancient Russian land that is the home of the Joint Institute for Nuclear Research" and became the namesake of moscovium.
The Dubna–Livermore collaboration strengthened their claim to the discoveries of moscovium and nihonium by conducting chemical experiments on the finaldecay product268Db. None of the nuclides in this decay chain were previously known, so existing experimental data was not available to support their claim. In June 2004 and December 2005, the presence of adubnium isotope was confirmed by extracting the final decay products, measuringspontaneous fission (SF) activities and using chemical identification techniques to confirm that they behave like agroup 5 element (as dubnium is known to be in group 5 of the periodic table).[1][56] Both the half-life and the decay mode were confirmed for the proposed268Db, lending support to the assignment of the parent nucleus to moscovium.[56][57] However, in 2011, theIUPAC/IUPAP Joint Working Party (JWP) did not recognize the two elements as having been discovered, because current theory could not distinguish the chemical properties ofgroup 4 and group 5 elements with sufficient confidence.[58] Furthermore, the decay properties of all the nuclei in the decay chain of moscovium had not been previously characterized before the Dubna experiments, a situation which the JWP generally considers "troublesome, but not necessarily exclusive".[58]
Two heavier isotopes of moscovium,289Mc and290Mc, were discovered in 2009–2010 as daughters of thetennessine isotopes293Ts and294Ts; the isotope289Mc was later also synthesized directly and confirmed to have the same properties as found in the tennessine experiments.[7]
In 2011, theJoint Working Party of international scientific bodiesInternational Union of Pure and Applied Chemistry (IUPAC) andInternational Union of Pure and Applied Physics (IUPAP) evaluated the 2004 and 2007 Dubna experiments, and concluded that they did not meet the criteria for discovery. Another evaluation of more recent experiments took place within the next few years, and a claim to the discovery of moscovium was again put forward by Dubna.[58] In August 2013, a team of researchers atLund University and at theGesellschaft für Schwerionenforschung (GSI) inDarmstadt,Germany announced they had repeated the 2004 experiment, confirming Dubna's findings.[59][60] Simultaneously, the 2004 experiment had been repeated at Dubna, now additionally also creating the isotope289Mc that could serve as a cross-bombardment for confirming the discovery of thetennessine isotope293Ts in 2010.[61] Further confirmation was published by the team at theLawrence Berkeley National Laboratory in 2015.[62]
In December 2015, the IUPAC/IUPAP Joint Working Party recognized the element's discovery and assigned the priority to the Dubna-Livermore collaboration of 2009–2010, giving them the right to suggest a permanent name for it.[63] While they did not recognise the experiments synthesising287Mc and288Mc as persuasive due to the lack of a convincing identification of atomic number via cross-reactions, they recognised the293Ts experiments as persuasive because its daughter289Mc had been produced independently and found to exhibit the same properties.[61]
In May 2016,Lund University (Lund,Scania, Sweden) and GSI cast some doubt on the syntheses of moscovium and tennessine. The decay chains assigned to289Mc, the isotope instrumental in the confirmation of the syntheses of moscovium and tennessine, were found based on a new statistical method to be too different to belong to the same nuclide with a reasonably high probability. The reported293Ts decay chains approved as such by the JWP were found to require splitting into individual data sets assigned to different tennessine isotopes. It was also found that the claimed link between the decay chains reported as from293Ts and289Mc probably did not exist. (On the other hand, the chains from the non-approved isotope294Ts were found to becongruent.) The multiplicity of states found when nuclides that are noteven–even undergo alpha decay is not unexpected and contributes to the lack of clarity in the cross-reactions. This study criticized the JWP report for overlooking subtleties associated with this issue, and considered it "problematic" that the only argument for the acceptance of the discoveries of moscovium and tennessine was a link they considered to be doubtful.[64][65]
On June 8, 2017, two members of the Dubna team published a journal article answering these criticisms, analysing their data on the nuclides293Ts and289Mc with widely accepted statistical methods, noted that the 2016 studies indicating non-congruence produced problematic results when applied to radioactive decay: they excluded from the 90% confidence interval both average and extreme decay times, and the decay chains that would be excluded from the 90% confidence interval they chose were more probable to be observed than those that would be included. The 2017 reanalysis concluded that the observed decay chains of293Ts and289Mc were consistent with the assumption that only one nuclide was present at each step of the chain, although it would be desirable to be able to directly measure the mass number of the originating nucleus of each chain as well as the excitation function of the243Am+48Ca reaction.[66]
UsingMendeleev's nomenclature for unnamed and undiscovered elements, moscovium is sometimes known aseka-bismuth. In 1979, IUPAC recommended that theplaceholdersystematic element nameununpentium (with the corresponding symbol ofUup)[67] be used until the discovery of the element is confirmed and a permanent name is 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 (for whom is was not created anyway), who called it "element 115", with the symbol ofE115,(115) or even simply115.[1]
On 30 December 2015, discovery of the element was recognized by theInternational Union of Pure and Applied Chemistry (IUPAC).[68] According to IUPAC recommendations, the discoverer(s) of a new element has the right to suggest a name.[69] A suggested name waslangevinium, afterPaul Langevin.[70] Later, the Dubna team mentioned the namemoscovium several times as one among many possibilities, referring to theMoscow Oblast where Dubna is located.[71][72] This name had previously been considered by the JINR for element 116, but it was then decided to name that elementlivermorium.[73]
In June 2016, IUPAC endorsed the latter proposal to be formally accepted by the end of the year, which it was on 28 November 2016.[11] The naming ceremony for moscovium, tennessine, and oganesson was held on 2 March 2017 at theRussian Academy of Sciences inMoscow.[74]
In 2024, the team at JINR reported the observation of one decay chain of289Mc while studying the reaction between242Pu and50Ti, aimed at producing more neutron-deficientlivermorium isotopes in preparation for synthesis attempts of elements119 and120. This was the first successful report of a charged-particle exit channel – the evaporation of a proton and two neutrons, rather than only neutrons, as the compound nucleus de-excites to theground state – in a hot fusion reaction between an actinide target and a projectile with atomic number greater than or equal to 20.[75] Such reactions have been proposed as a novel synthesis route for yet-undiscovered isotopes of superheavy elements with several neutrons more than the known ones, which may be closer to the theorizedisland of stability and have longer half-lives. In particular, the isotopes291Mc–293Mc may be reachable in these types of reactions within current detection limits.[76][77]
Very few properties of moscovium or its compounds have been measured; due to its extremely limited and expensive production[17] and the fact that it decays very quickly. A few singular properties have been measured, but for the most part, properties of moscovium remain unknown and only predictions are available.
The expected location of the island of stability. The dotted line is the line ofbeta stability.
Moscovium is expected to be within anisland of stability centered oncopernicium (element 112) andflerovium (element 114).[78][79] Due to the expected high fission barriers, any nucleus within this island of stability exclusively decays by alpha decay and perhaps some electron capture andbeta decay.[2] Although the known isotopes of moscovium do not actually have enough neutrons to be on the island of stability, they can be seen to approach the island as in general, the heavier isotopes are the longer-lived ones.[7][8][56]
The hypothetical isotope291Mc is an especially interesting case as it has only one neutron more than the heaviest known moscovium isotope,290Mc. It could plausibly be synthesized as the daughter of295Ts, which in turn could be made from the reaction249Bk(48Ca,2n)295Ts.[78] Calculations show that it may have a significantelectron capture orpositron emission decay mode in addition to alpha decay and also have a relatively long half-life of several seconds. This would produce291Fl,291Nh, and finally291Cn 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. Possible drawbacks are that thecross section of the production reaction of295Ts is expected to be low and the decay properties of superheavy nuclei this close to the line ofbeta stability are largely unexplored.[78] The heavy isotopes from291Mc to294Mc might also be produced using charged-particle evaporation, in the245Cm(48Ca,pxn) and248Cm(48Ca,pxn) reactions.[76][77]
The isotope286Mc was found in 2021 at Dubna, in the243Am(48Ca,5n)286Mc reaction: it decays into the already-known282Nh and its daughters.[80] The undiscovered light isotopes284Mc and285Mc could be synthesized in the241Am+48Ca reaction. They are predicted to undergo a chain of alpha decays, ending at transactinide isotopes too light to be produced by hot fusion and too heavy to be produced by cold fusion.[78] The yet-lighter282Mc and283Mc could be synthesized in the243Am+44Ca, but the cross section would likely be lower.[78]
Other possibilities to synthesize nuclei on the island of stability include quasifission (partial fusion followed by fission) of a massive nucleus.[81] Such nuclei tend to fission, expelling doublymagic or nearly doubly magic fragments such ascalcium-40,tin-132,lead-208, orbismuth-209.[82] 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,[81] although formation of the lighter elementsnobelium orseaborgium is more favored.[78] 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.[78] 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.[78]
In theperiodic table, moscovium is a member of group 15, the pnictogens. It appears belownitrogen,phosphorus,arsenic,antimony, and bismuth. Every previous pnictogen has five electrons in its valence shell, forming avalence electron configuration of ns2np3. In moscovium's case, the trend should be continued and the valence electron configuration is predicted to be 7s27p3;[1] therefore, moscovium will behave similarly to its lightercongeners in many respects. However, notable differences are likely to arise; a largely 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.[83] In relation to moscovium 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.[84] 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.[83][l] For many theoretical purposes, the valence electron configuration may be represented to reflect the 7p subshell split as 7s2 7p2 1/27p1 3/2.[1] These effects cause moscovium's chemistry to be somewhat different from that of its lightercongeners.
The valence electrons of moscovium fall into three subshells: 7s (two electrons), 7p1/2 (two electrons), and 7p3/2 (one electron). The first two of these are relativistically stabilized and hence behave asinert pairs, while the last is relativistically destabilized and can easily participate in chemistry.[1] (The 6d electrons are not destabilized enough to participate chemically.)[2] Thus, the +1oxidation state should be favored, likeTl+, and consistent with this the firstionization potential of moscovium should be around 5.58 eV, continuing the trend towards lower ionization potentials down the pnictogens.[1] Moscovium and nihonium both have one electron outside a quasi-closed shell configuration that can bedelocalized in the metallic state: thus they should have similarmelting andboiling points (both melting around 400 °C and boiling around 1100 °C) due to the strength of theirmetallic bonds being similar.[2] Additionally, the predicted ionization potential,ionic radius (1.5 Å for Mc+; 1.0 Å for Mc3+), andpolarizability of Mc+ are expected to be more similar to Tl+ than its true congenerBi3+.[2] Moscovium should be a dense metal due to its highatomic weight, with a density around 13.5 g/cm3.[2] The electron of thehydrogen-like moscovium atom (oxidized so that it only has one electron, Mc114+) is expected to move so fast that it has a mass 1.82 times that of a stationary electron, due torelativistic effects. For comparison, the figures for hydrogen-like bismuth and antimony are expected to be 1.25 and 1.077 respectively.[83]
Moscovium is predicted to be the third member of the 7p series ofchemical elements and the heaviest member of group 15 in the periodic table, belowbismuth. Unlike the two previous 7p elements, moscovium is expected to be a good homologue of its lighter congener, in this case bismuth.[85] In this group, each member is known to portray the group oxidation state of +5 but with differing stability. For nitrogen, the +5 state is mostly a formal explanation of molecules likeN2O5: it is very difficult to have fivecovalent bonds to nitrogen due to the inability of the small nitrogen atom to accommodate fiveligands. The +5 state is well represented for the essentially non-relativistic typical pnictogensphosphorus,arsenic, andantimony. However, for bismuth it becomes rare due to the relativistic stabilization of the 6s orbitals known as theinert-pair effect, so that the 6s electrons are reluctant to bond chemically. It is expected that moscovium will have an inert-pair effect for both the 7s and the 7p1/2 electrons, as thebinding energy of the lone 7p3/2 electron is noticeably lower than that of the 7p1/2 electrons. Nitrogen(I) and bismuth(I) are known but rare and moscovium(I) is likely to show some unique properties,[86] probably behaving more like thallium(I) than bismuth(I).[2] Because of spin-orbit coupling,flerovium may display closed-shell or noble gas-like properties; if this is the case, moscovium will likely be typically monovalent as a result, since the cation Mc+ will have the same electron configuration as flerovium, perhaps giving moscovium somealkali metal character.[2] Calculations predict that moscovium(I) fluoride and chloride would be ionic compounds, with an ionic radius of about 109–114 pm for Mc+, although the 7p1/2 lone pair on the Mc+ ion should be highlypolarisable.[87] The Mc3+ cation should behave like its true lighter homolog Bi3+.[2] The 7s electrons are too stabilized to be able to contribute chemically and hence the +5 state should be impossible and moscovium may be considered to have only three valence electrons.[2] Moscovium would be quite a reactive metal, with astandard reduction potential of −1.5 V for the Mc+/Mc couple.[2]
The chemistry of moscovium inaqueous solution should essentially be that of the Mc+ and Mc3+ ions. The former should be easilyhydrolyzed and not be easilycomplexed withhalides,cyanide, andammonia.[2] Moscovium(I)hydroxide (McOH),carbonate (Mc2CO3),oxalate (Mc2C2O4), andfluoride (McF) should be soluble in water; thesulfide (Mc2S) should be insoluble; and thechloride (McCl),bromide (McBr),iodide (McI), andthiocyanate (McSCN) should be only slightly soluble, so that adding excesshydrochloric acid would not noticeably affect the solubility of moscovium(I) chloride.[2] Mc3+ should be about as stable as Tl3+ and hence should also be an important part of moscovium chemistry, although its closesthomolog among the elements should be its lighter congener Bi3+.[2] Moscovium(III) fluoride (McF3) andthiozonide (McS3) should be insoluble in water, similar to the corresponding bismuth compounds, while moscovium(III) chloride (McCl3), bromide (McBr3), and iodide (McI3) should be readily soluble and easily hydrolyzed to formoxyhalides such as McOCl and McOBr, again analogous to bismuth.[2] Both moscovium(I) and moscovium(III) should be common oxidation states and their relative stability should depend greatly on what they are complexed with and the likelihood of hydrolysis.[2]
Like its lighter homologuesammonia,phosphine,arsine,stibine, andbismuthine, moscovine (McH3) is expected to have atrigonal pyramidal molecular geometry, with an Mc–H bond length of 195.4 pm and a H–Mc–H bond angle of 91.8° (bismuthine has bond length 181.7 pm and bond angle 91.9°; stibine has bond length 172.3 pm and bond angle 92.0°).[88] In the predictedaromatic pentagonal planarMc− 5 cluster, analogous topentazolate (N− 5), the Mc–Mc bond length is expected to be expanded from the extrapolated value of 312–316 pm to 329 pm due to spin–orbit coupling effects.[89]
The isotopes288Mc,289Mc, and290Mc have half-lives long enough for chemical investigation.[90] A 2024 experiment at the GSI, producing288Mc via the243Am+48Ca reaction, studied the adsorption of nihonium and moscovium on SiO2 and gold surfaces. The adsorption enthalpy of moscovium on SiO2 was determined experimentally as−ΔHSiO2 ads(Mc) = 54+11 −5 kJ/mol (68% confidence interval). Moscovium was determined to be less reactive with the SiO2 surface than its lighter congener bismuth, but more reactive than closed-shell copernicium and flerovium. This arises because of the relativistic stabilisation of the 7p1/2 shell.[91]
^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[12] or112;[13] sometimes, the term is presented an equivalent to the term "transactinide", which puts an upper limit before the beginning of the hypotheticalsuperactinide series).[14] 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.[15] 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.[16]
^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.[20]
^This figure also marks the generally accepted upper limit for lifetime of a compound nucleus.[25]
^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.[27] 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.[28]
^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.[40]
^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.[45] The first direct measurement of mass of a superheavy nucleus was reported in 2018 at LBNL.[46] 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).[47]
^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).[36] 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,[48] a leading scientist at JINR, and thus it was a "hobbyhorse" for the facility.[49] 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.[25] They thus preferred to link new isotopes to the already known ones by successive alpha decays.[48]
^For instance, element 102 was mistakenly identified in 1957 at the Nobel Institute of Physics inStockholm,Stockholm County,Sweden.[50] 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.[51] 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.[51] JINR insisted that they were the first to create the element and suggested a name of their own for the new element,joliotium;[52] the Soviet name was also not accepted (JINR later referred to the naming of the element 102 as "hasty").[53] This name was proposed to IUPAC in a written response to their ruling on priority of discovery claims of elements, signed 29 September 1992.[53] The name "nobelium" remained unchanged on account of its widespread usage.[54]
^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.
^abcdefghijklHoffman, 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.
^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.
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^"115-ый элемент Унунпентиум может появиться в таблице Менделеева".oane.ws (in Russian). 28 August 2013. Retrieved2015-09-23.В свою очередь, российские физики предлагают свой вариант – ланжевений (Ln) в честь известного французского физика-теоретика прошлого столетия Ланжевена.
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