The Road to the Island of Stability
• Physics 17, 150
Scientists have created an isotope of the superheavy element livermorium using a new fusion reaction. The result paves the way for the discovery of new chemical compounds.
APS/Carine Cain
How and where in the Universe are chemical elements formed? How can we explain their relative abundance? What is the maximum number of protons and neutrons that nuclear energy can combine in one nucleus? Nuclear physicists and chemists hope to find answers to such questions by making and learning new things. But as the elements increase, they become more difficult to combine. The heaviest elements discovered so far have been created by high atomic number explosions (high-Z) actinide targets with calcium-48 beams (48Ca). This isotope is particularly suitable for such experiments because of its unique nuclear configuration, in which the number of neutrons and protons are “magic numbers.” However this method was not able to produce particles exceeding oganesson (proton number, Z = 118). Now a team at the Lawrence Berkeley National Laboratory (LBNL), in California, has created a very heavy compound, livermorium-290 (Z = 116), using a titanium-50 lamp, which is not double magic [1]. By removing the need for two magic nuclei, the work opens up new ways to produce more than 118 units.
The heaviest natural element in abundance on Earth and in the Solar System is uranium, with an atomic number of 92. Stars are the main places for the natural production of naturally occurring elements. During its lifetime, a star can form atomic nuclei up to iron (Z = 26) in the fusion reaction. Nuclei exceeding iron are produced at the end of the star’s life, the merger of supernovae or neutron-star – violent events that produce free neutrons. [2]. These neutrons are captured by the “seed nuclei” of the metal, and beta decay converts some of the neutrons into protons, thereby increasing the atomic number and creating elements in reach uranium.Z = 92). Perhaps, this process of capturing neutrons can lead to very heavy nuclei, which enter the depths of the region of the heaviest elements with atomic numbers greater than 100. Now the periodic table it contains 26 more elements than synthetic uranium. However, we do not know how many of them may occur naturally.
All of the heaviest matter known today was created by facilitating the fusion reaction between lighter nuclei and stronger nuclei. [3]. The formation of supermassive matter is a rare event. For example, to realize one nucleus of element 118, the target foil must be bombarded with billions of billions. In a typical trial, this takes two weeks. To produce one gram of this substance will require more than 1019 years, corresponding to a billion times the age of our Universe. However, at the end of this production process, you will have nothing to show for it. This is because the heavier particles pass through faster: They all have short half-lives, some as short as a millionth of a second – long enough to from where they started to the detectors, but they are too short to make even microscopic. pieces of matter. This suggests the challenges that researchers face in this field.
Experiments have shown that the products of the heaviest fusion are greatest when the proton or nucleus is considered to be the so-called double magic nucleus—a nucleus with proton and neutron shells. This property improves not only their stability but also the stability of fusion products. All elements with atomic numbers 107 and above were discovered by the collision of such nuclei. Elements 107 to 113 were discovered by experiments in which double magic leads to isotopes. 208Pb (82 protons, 126 neutrons) was used as target material. [4, 5]while elements 114 to 118 were discovered through a fusion reaction between an actinide target and a double isotope of calcium. 48Ca (20 protons, 28 neutrons) [6].
The main goal of today’s search for the heaviest element is to combine elements 119 and 120. Element 120 is very interesting because some types of theories predict a region of enhanced stability of nuclei and near this number of protons, the so-called stability island. [7]. This improved stability does not mean that these nuclei are not radioactive. They are, but their half-lives are expected to be longer than those of other heavier isotopes. If this island of stability exists, it can be achieved through the process of neutron capture from dying stars.
Production yields of sections 119 and 120 may be small. The researchers expect that the experiment will have to take half a year or more to see a single nucleus. But they are not the only problem. When we try to combine these elements, we face another challenge: The 48The Ca projectiles favored by researchers no longer work because there are no proper materials to assemble them. Access Z value 119 and 120 use a 48Ca beam will require einsteinium targets (Z = 99) and fermium (Z = 100), respectively. These unstable nuclei have a half-life shorter than the length of the experiment, and are only available in microgram quantities—far less than the 10 or milligrams required. Instead, we must enter the unknown, and use nonmagic projectiles and nuclei. “Leaps into the unknown” were made in the last decade by researchers in other laboratories (see Reference [8] and references therein), but clear evidence of the sought-after sections 119 and 120 did not appear.
The LBNL team adopted a systematic, step-by-step method, which does not target more than 118 elements but for the isotopes of an element already known to be extremely heavy: livermorium (Z = 116, with four known isotopes). The third heaviest element on the current periodic table, livermorium, was discovered in 2004 by a Russian-American collaboration at Russia’s Flerov Laboratory of Nuclear Reactions (FLNR) in experimental studies. 48Ca projectiles and curium targets [9].
LBNL researchers sought to create livermorium using an untested compound. They attacked plutonium targets in 50The projectiles—both rare nuclei—and observed two nuclei of the livermorium isotope 290Lv. This marks the first time that one of the heaviest objects known has been created in a collisionless system, making the experiment an important proof of principle. The result shows that the combined reaction of the mysterious nuclei has the potential to produce isotopes of the heaviest elements known, and one can expect, of new elements.
As well as enabling the discovery of new elements, actions with rare projectiles provide the opportunity to find many new isotopes of known elements with atomic numbers from 104 to of 118. There are 110 different isotopes known so far. About 50 other isotopes are expected to exist but are not accessible through the conventional fusion reaction used. 208Pb goals or 48Of the beams. Applications involving non-magical systems can allow this gap to be filled. It is important to note that the FLNR has also published results on the production of element 116 in collisions involving a nucleus twice as heavy. 48Ca [10]. Using the fusion reaction of 54Cr and 238U, FLNR claims discovery of new isotope of element 116 (288Lv), but the results have not yet appeared in a peer-reviewed publication.
References
- JM Gates and al.“Discovery of new substances: The production of livermorium (Z = 116) and 50Go,” Phys. Pastor Lett. 133172502 (2024).
- K. Langanke and F.-K. Thielemann, “Making Parts of the Universe,” Europhys. News 4423 (2013).
- P. Armbruster and G. Münzenberg, “Experimental method opens up world of supercritical particles,” EUR. Phys. J.H 37237 (2012).
- S. Hofmann, “Discovery of parts 107 to 112,” EPJ Web Conf. 13106001 (2016).
- K. Morita and al.“Try the combination of element 113 on the reaction 209Bi(70Zn,n)278113,” J. Phys. Soc. Jpn. 732593 (2004).
- Yu. Ts. Oganesian and VK Utyonkov, “Super-heavy element research,” Rep. Prog. Phys. 78036301 (2015).
- Yu. Ts. Oganesian and KP Rykaczewski, “The beach on the island of stability,” Phys. Today 6832 (2015).
- S. Hofmann and al.“Exploration of the heaviest nuclei and search for element 120,” EUR. Phys. J.A 52180 (2016).
- Yu. Ts. Oganisian and al.“Differential parameters for fusion-evaporation reactions 244Pu (48CA,xn)292−x114 and 245Cm(48Ca,xn)293−x116,” Phys. Pastor C 69054607 (2004).
- Joint Institute for Nuclear Research, “Livermorium-288 made world first at JINR Laboratory of Nuclear Reactions” 23 October 2023; https://www.jinr.ru/posts/v-lyar-oiyai-vpervye-v-mire-sintezirovan-livermorij-288/.
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