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HK: Physik der Hadronen und Kerne
HK 41: Kernphysik V / Spektroskopie II
HK 41.9: Group Report
Wednesday, March 24, 1999, 17:45–18:15, B
Structure and Formation Mechanism of the Transfermium Isotope 254No — •Peter Reiter1,2, T.L. Khoo2, C.J. Lister2, D. Seweryniak2, I. Ahmad2, M.P. Carpenter2, J.A. Cizewski2,3, C.N. Davids2, J.P. Greene2, W.F. Henning2, R.V.F. Janssens2, T. Lauritsen2, S. Siem2,4, A.A. Sonzogni2, J. Uusitalo2, I. Wiedenhöver2, N. Amzal5, P.A. Butler5, A.J. Chewter5, K.Y. Ding3, N. Fotiades3, P.T. Greenlees5, R.-D. Herzberg5, G.D. Jones5, W. Korten6, M. Leino7, and K. Vetter8 — 1Sektion Physik, LMU München — 2Argonne National Laboratory — 3Rutgers University — 4University of Oslo — 5University of Liverpool — 6DAPNIA/SPhN, CEA Saclay — 7University of Jyvaskyla — 8Lawrence Berkeley National Laboratory
A first experiment was performed using the Gammasphere- Fragment
Mass Analyzer combination to produce 254No via the
208Pb(48Ca,2n) reaction at a bombarding energy of 215 MeV.
The Z=102 isotope 254No has a small cross section ≈3µb
and was identified by measuring the alpha decay chain
254No→ 250Fm→246Cf.
Despite the long half life of 254No (t1/2=55s),
the recoil decay tagging technique was exploited.
γ transitions from the rotational ground state band has been
identified up to spin 14, indicating that the nucleus is deformed.
The deduced quadrupole deformation β =0.27 is in agreement
with theoretical predictions. These observations confirm that the
shell-correction energy responsible for the stability of
transfermium nuclei is partly derived from deformation.
The spin distribution for the evaporation residues was measured.
Information on the fission barrier, its angular dependence, and the
reaction mechanism was obtained and will be discussed.
Supported by U.S. Department of Energy, Contract Nos. W-31-109-ENG-38,
DEFG05-88ER40411 and by the National Science Foundation.