Synthesi of new elements

In the early years of this century the periodic table ended with element 92 but, with J. Chadwick s discovery of the neutron in 1932 and the realization that neutron-capture by a heavy atom is frequently followed by j6 emission yielding the next higher element, the synthesis of new elements became an exciting possibility. E. Fermi and others were quick to attempt the synthesis of element 93 by neutron bombardment of but it gradually became evident that the main result of the process was not the production of element 93 but nuclear fission, which produces lighter elements. However, in 1940, E. M. McMillan and P. H. Abelson in Berkeley, California, were able to identify, along with the fission products, a short-lived isotope of... 

Experimental studies soon confirmed all these expectations. The most powerful tool in achieving these results was the cyclotron. Ernest O. Lawrence, its inventor, was born in Canton, South Dakota, on August 8, 1901. He was educated at St. Olaf College and the University of South Dakota, and did graduate work in physics at Minnesota, Chicago, and Yale. The latter university gave him his doctorate in 1925. He remained at Yale until 1928, and was then called to the University of California at Berkeley, where he still remains as Director of the Radiation Laboratory. He received the Nobel Prize in Physics in 1939. It was due to Lawrence and the cyclotron that California became the outstanding center for the synthesis of new elements, which it still remains (I). 

The main fields of application of heavy ions are synthesis of new elements (superheavy elements), production of nuclides far away from the line of ji stability (exotic nuclides), investigation of nuclear matter at high densities, production of small holes of certain diameters in thin foils and irradiation of tumours in medicine. 

Synthesis of new elements up to Z 120 can be expected by application of cold fusion and refined techniques. 

One of most important aspects of the Cold War was the race to develop and deploy nuclear weapons. The early arms race was largely focused on nuclear fission, but by the 1950s the much more powerful fusion weapons were the main area of development. The competition, however, was not only military, and the quest for new elements became a minor but important competition, primarily between American laboratories and Soviet ones. Because the equipment used to do nuclear research was used to produce elements and material for weapons, the link between the synthesis of new elements and the arms race was direct if one side could produce a new element, it revealed that that side s equipment, resources, and scientists had an advantage over the opposition. Since the equipment, resources, and scientists were also part of the nuclear arms development system, the implication was that the advantage would extend to the weapons. Even without the arms race, the competition to synthesize new elements was fierce, since international scientific status and even Nobel Prizes could be gained by such work. 

At this point, the synthesis of new elements stopped. The reason is that nuclei larger than those of hydrogen and helium can form only when like-charged particles (such as protons or helium nuclei) combine to form heavier nuclei. A hypothetical example is the formation of a beryllium nucleus by the combination of two helium nuclei ... 

Summary. The synthesis of new elements takes place inside stars. How do stars evolve and distribute this creation to the universe at large This article starts with the observables that the theory of stellar evolution aims to reproduce, and gives a quick overview of what that theory predicts (Sects. 2-3). It presents the equations governing stellar structure and evolution (Sects. 4-6) and the physics of stellar interiors (Sects. 7-9). Approximate and numerical methods for their solution are outlined (Sects. 10-11) and the general results of stellar structure and evolution are discussed (Sects. 12-13). The structure and evolution of horizontal-branch stars, hydrogen-deficient stars and other stelfar remnants are also considered (Sects. 14-15). 

The second part of the book comprising two chapters (Chapters 12 and 13) is devoted to synthesized elements. In Chapter 12 the reader will be introduced to the synthesis of new elements within the previous boundaries of the periodic system—from hydrogen to uranium (technetium, promethium, astatine, francium). Chapter 13 covers the history of transuranium elements and prospects of nuclear synthesis. 

Oganessian, Yu.Ts, Lazarev, Yu.A Problems involved in the synthesis of new elements. Pure Appl. Chem. 53, 925-947 (1981)... 

Von Oertzen, W. Cold multi-nucleon transfer between heavy nuclei and the synthesis of new elements. Z. Phys. A342, 177-182 (1992)... 

Work at Berkeley-Livermore in 1974 first convincingly demonstrated the synthesis of this element via the reaction " Cf( 0,4n) 106. Contemporaneous work at Dubna applied their novel cold fusion method (p. 1280) to reactions such as 82 Pb - - 24 Cr although this methodolgy was crucial to the synthesis of all later elements (107-112) it did not at that time demonstrate the formation of element 106 with adequate conviction. Very recently, element 106 was resynthesized by a new group at Berkeley using exactly the same reaction as employed in 1974. The isotope 106 decays with a half-life of 0.8 0.2 s to 104 and then by a second... 

F. Joliot and Irene Joliot-Curie (Paris) synthesis of new radioactive elements. 

Although much of the preceding discussion involved the synthesis of new molecules by organic and inorganic chemists, there is another area of chemistry in which such creation is important—the synthesis of new atoms. The periodic table lists elements that have been discovered and isolated from nature, but a few have been created by human activity. Collision of atomic particles with the nuclei of existing atoms is the normal source of radioactive isotopes and of some of the very heavy elements at the bottom of the periodic table. Indeed nuclear chemists and physicists have created some of the most important elements that are used for nuclear energy and nuclear weapons, plutonium in particular. 

Controversy about the first synthesis of new chemical elements in the trans-lawrencium region has recently been resolved by a joint lUPAC and lUPAP (International Union of Pure and Applied Physics) committee. CNIC has assigned names that appear to have been internationally accepted for these elements. Although I have relied on the lUPAC/IUPAP document to discuss elements up to Meitnerium, for elements above Z = 109, the analysis provided is strictly my own due to my reading and interpretation of the scientific literature. 

From ancient times, humans have pondered what the universe is made of Early philosophers proposed fire, earth, water, and air either individually or in combination as the building blocks of nature. Lavoisier defined an element operationally as a substance that cannot be broken down chemically. Using this definition, the number of elements has increased from around 30 in Lavoisier s time to over 115 today. The initial search for elements involved classical methods such as replacement reactions, electrochemical separation, and chemical analysis. New methods such as spectroscopy greatly advanced the discovery of new elements during the twentieth century. The last half century has been marked by the synthesis of elements by humans. 

---