Criteria for the Discovery of Chemical Elements

Chemistry of Superheavy Elements

“…2) Following arguments given in ref. [45,91] only those composite nuclear systems that live at least 10 À14 s shall be considered a chemical element. This time is well justified from nuclear aspects, for example, from maximum lifetimes of excited compound nuclei (see Section 2.2), as well as from chemical aspects, for example, from the minimum formation time of a molecule such as hydrogen.…”

Theory of molecular-orbital and compound-nucleus x-ray emission in heavy-ion-atom collisions with nuclear sticking

“…We therefore suggest that experiments that measure x-rays in coincidence with fusionfission reaction products should be attempted [41]. Finally we would like to comment on the question of what constitutes the creation of a superheavy element [40]. A very basic criterion is that one actually forms an atom, though the charge state of the atom need not be zero.…”

“…Our work shows that as long as the K electron has time to orbit the CN approximately 3 times (20/2n, putting c%~,,~coK, the K-electron binding frequency), one can say that the K shell has been formed, with a width of less than 5~o. Harvey et al [40] have suggested that the measurement of the atomic number of the UA by e.g. identification of the UA x-rays of c~ decay products, is one of the basic criteria for claiming the discovery of a new element.…”

Discovery of scandium, titanium, mercury, and einsteinium isotopes

“…While the criteria for the discovery of an element are well established [91][92][93] the criteria for the discovery or even the existence of an isotope are not well defined (see, for example, the discussion in Ref. [53]).…”