Artificial radioactive element properties unknown	memory peg
	1994 Sigurd Hofmann and co-workers, Darmstadt, Germany
	Darmstadt, town in Germany

First prepared in 1994 by Sigurd Hofmann, Victor Ninov, Fritz Peter Heßberger, Peter Armbruster, H. Folger, Gottfried Münzenberg, H.J. Schött (Gesellschaft für Schwerionenforschung, Darmstadt, Germany), Andre Georgievich Popeko, Alexander Vladimirovich Yeremin, A.N. Andreyev (Лаборатория ядерных реакций им. Г.Н. Флерова / Flerov Laboratory of Nuclear Reactions, FLNR - ОИЯИ / JINR, Дубна (Dubna), Russia), S. Saro, Rudolf Janik (Katedra jadrovej fyziky, Univerzita Komenského, Bratislava, Slovakia), and Matti Leino (Fysiikan laitos, Jyväskylän Yliopisto, Finland).

The element does not have a name yet, therefore the systematic IUPAC name is used (system explained below).

Production and Decay of ²⁶⁹110 (Abstract)

In an experiment carried out to identify element 110, we have observed an alpha-decay chain, that can be unambiguously assigned to ²⁶⁹110. In a series of preexperiments the excitation functions of the fusion reactions

⁵⁰Ti + ²⁰⁸Pb → ²⁵⁸104*

and

⁵⁸Fe + ²⁰⁸Pb → ²⁶⁶108*

were measured with high precision in order to get the optimum projectile energies for the production of these heavy elements. The cross-section maxima of the 1n evaporation channels were observed at excitation energies of 15.6 MeV and 13.4 MeV, respectively. These data result in an optimum excitation energy of 12.3 MeV of the compound nucleus for the production of ²⁶⁹110 in the reaction

⁶²Ni + ²⁰⁸Pb → ²⁶⁹110 + 1n

In irradiations at the corresponding beam energy of 311 MeV we have observed a decay chain of 4 subsequent alpha decays. This can be assigned to the isotope with the mass number 269 of the element 110 on the basis of delayed α-α coincidences. The accurately measured decay data of the daughter isotopes of the elements 108 to 102, obtained in the previous experiments, were used. The isotope 269-110 decays with a half-life of (270 +1300 -120) micro seconds by emission of (11.132+-0.020) MeV alpha particles. The production cross-section is (3.3 +6.2 -2.7) pb.

IUPAP/IUPAC Joint working party assessment: Element 110 has been discovered by this collaboration (Karol et al., 2001, 961).

Our Berkeley group believes that element 110 should receive the name 'hahnium,' in honour of the scientific giant 'Otto Hahn.' This also has the advantage that it would then not be necessary for so many of us to continue to use the name 'Hahnium' for element 105 to honor Otto Hahn.

"Element 105 had by then been renamed Dubnium (after its place of discovery, Dubna in the USSR), and Element 110 was finally named Darmstadtium in 2003 (again after its place of discovery, Darmstadt, Germany). In 1994, Element 108 was named Hahnium, symbol Ha, by CNIC and IUPAC (International Union of Pure and Applied Chemistry), but this was subsequently renamed Hassium (after the German state of Hesse in which Darmstadt is found). Despite these attempts at atomic longevity, Hahn, the co-discoverer of nuclear fission, and Nobel Prize Winner (1944, Chemistry) now no longer resides in an elemental name, although Germany's first nuclear ship was called the Otto Hahn." (note):

In January 2003 IUPAC recommended the name Darmstadtium, symbol Ds, for element 110: "A joint IUPAC-IUPAP Working Party (JWP) has confirmed the discovery of element number 110 and this by the collaboration of Hofmann et al. from the Gesellschaft für Schwerionenforschung mbH (GSI) in Darmstadt, Germany. In accord with IUPAC procedures, the discoverers have proposed a name and symbol for the element. The Inorganic Chemistry Division Committee now recommends this proposal for acceptance. The proposed name is darmstadtium with symbol Ds. This proposal lies within the long established tradition of naming an element after the place of its discovery." (PDF file on-line).

Further reading (Ununnilium):

• S. Hofman et al., "Production and Decay of ²⁶⁹110." Zeitschrift für Physik A 350 (1995), 277-280 (Submitted November 14, 1994) (Abstract on-line).
• P.J. Karol, H. Nakahara, B.W. Petley, & E. Vogt, On the Discovery of the Elements 110–112 (IUPAC Technical Report). Pure Appl.Chem. 73, 6 (2001), pp.959–967 (PDF file on-line).

Last update:
© Peter van der Krogt