Dresden 2000 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 10: Kernphysik / Spektroskopie II

HK 10.8: Vortrag

Montag, 20. März 2000, 18:45–19:00, B 68

Fission Barrier and High Angular Momentum States of Z=102 Nobelium Isotopes — •Peter Reiter^1,2, T.L. Khoo², T. Lauritsen², C.J. Lister², D. Seweryniak², I. Ahmad², N. Amzal³, P. Bhattacharyya², P.A. Butler³, M.P. Carpenter², A.J. Chewter³, J.A. Cizewski^2,4, C.N. Davids², J.P. Greene², P.T. Greenlees³, A. Heinz², W.F. Henning², R.-D. Herzberg³, R.V.F. Janssens², G.D. Jones³, F.G.. Kondev², M. Leino⁵, S. Siem^2,6, A.A. Sonzogni², J. Uusitalo^2,5, K. Vetter⁷, and I. Wiedenhöver² — ¹Sektion Physik, LMU München — ²Argonne National Laboratory — ³University of Liverpool — ⁴Rutgers University — ⁵University of Jyvaskyla — ⁶University of Oslo — ⁷Berkeley National Laboratory

Excited states in ^253,254No were produced via ⁴⁸Ca induced reactions on ^207,208Pb targets. Gammasphere was used to measure not only the discrete γ rays, but also the γ-ray multiplicity and sum energy. The γ rays from nobelium nuclei were identified from a high fission background by requiring coincidences with evaporation residues. The latter were identified with the Argonne fragment mass analyzer. The ground-state band of ²⁵⁴No has been identified up to spin 20. The entry distribution in angular momentum and excitation energy for formation of ²⁵⁴No has been measured for two excitation energies. This nucleus survives up to spin 22 ℏ and excitation energy >6 MeV above the yrast line, implying that the shell-correction energy persists to high spin. Experimental values for the shell correction are provided. Comparable results are obtained for the odd neighbour isotope ²⁵³No.