Decay studies of K isomers in 254No

F. P. Heßberger; S. Antalic; B. Sulignano; D. Ackermann; S. Heinz; S. Hofmann; B. Kindler; J. Khuyagbaatar; I. Kojouharov; P. Kuusiniemi; M. Leino; B. Lommel; R. Mann; K. Nishio; A. G. Popeko; Š. Šáro; B. Streicher; J. Uusitalo; M. Venhart; A. V. Yeremin

doi:10.1140/epja/i2009-10899-9

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2023 Impact factor 2.6

Hadrons and Nuclei

Eur. Phys. J. A (2010) 43: 55-66
https://doi.org/10.1140/epja/i2009-10899-9

Regular Article - Experimental Physics

Decay studies of K isomers in ²⁵⁴No

F. P. Heßberger¹^*, S. Antalic², B. Sulignano¹^,a, D. Ackermann¹, S. Heinz¹, S. Hofmann¹^,3, B. Kindler¹, J. Khuyagbaatar¹^,4, I. Kojouharov¹, P. Kuusiniemi¹^,5, M. Leino⁶, B. Lommel¹, R. Mann¹, K. Nishio⁷, A. G. Popeko⁸, Š. Šáro², B. Streicher²^,1, J. Uusitalo⁶, M. Venhart² and A. V. Yeremin⁸

¹ GSI, Helmholtzzentrum für Schwerionenforschung GmbH, 64291, Darmstadt, Germany
² Department of Nuclear Physics and Biophysics, Comenius University Bratislava, 84248, Bratislava, Slovakia
³ Institut für Physik, Goethe-Universität Frankfurt, 60054, Frankfurt, Germany
⁴ St. Petersburg State University, 198504, Stari Peterhof, St. Petersburg, Russia
⁵ CUPP, University of Oulu, 90014, Oulu, Finland
⁶ Department of Physics, University of Jyväskylä, 40014, Jyväskylä, Finland
⁷ Japan Atomic Energy Agency, Tokai, 319-1184, Ibaraki, Japan
⁸ Flerov Laboratory of Nuclear Reactions, JINR, 141890, Dubna, Russia

^* e-mail: F.P.Hessberger@gsi.de

Received: 12 May 2009
Revised: 16 October 2009
Accepted: 15 November 2009
Published online: 15 December 2009

Abstract

A detailed $\gamma$ spectroscopic decay study of two K isomers in ²⁵⁴No was performed. In addition to the previously reported $\gamma$ lines two new transitions of E = 778 , 856keV could be attributed to the decay pattern of ^254m1No ( T _1/2 = 275±7 ms). The population of an excited band built up on this isomer ( $\ensuremath K^{\pi} =8^{-}$ by the decay of ^254m2No ( T _1/2 = 198±13 μs) could be proven by measuring delayed $\gamma$ - $\gamma$ coincidences between transitions stemming from the decay of both isomeric states. The energies of the band members could be established up to $\ensuremath I^{\pi} = 15^{-}$ . A spontaneous fission branch of (2.0±1.2)×10^-4 was measured for ^254m1No , an upper limit of $\le$ 1.2×10^-4 was estimated for ^254m2No . These values demonstrate the high stability of multi-quasiparticle configurations against spontaneous fission. Evidence for an $\alpha$ decay branch of ^254m1No in the order of 1×10^-4 was found.