Résumé du preprint DAPNIA-04-299

DAPNIA-04-299
Spectroscopy of the odd transfermium $^{251}$Md and $^{255}$Lr nuclei using $\gamma$, electron and \alpha$ spectroscopy
A. Chatillon, Ch. Theisen, E. Bouchez, E. Clement, R. Dayras, A. Drouart, A. G"orgen, A. Hurstel, W. Korten, Y. Le Coz, C. Simenel, J. Wilson, S. eckhaudt, T. Grahn, P.T. Greenlees, P. Jones, R. Julin, S. Juutinen, H. Kettunen, M. Leino, A-P. Leppanen, V. Maanselka, P. Nieminen, J. akarinen, J. Perkowski, P. Rahkila, J. Sare'n, C. Scholey, J. Uusitalo, K. Van de Vel, G. Auger, B. Bouriquet J.M. Casandjian, R. Cee, G. de France, R. de Tourreil, M.G. St Laurent, Ch. Stodel, A. Villari, M. Rejmund, N. Amzal, J.E. Bastin, P.A. Butler, R-D. Herzberg, P.J.C. Ikin, G.D. Jones, A. Pritchard, S. Gr'evy, K. Hauschild, A. Korichi. A. Lopez-Martens, F.P. Hessberger, S.M. Lukyanov, Yu. E. Penionzhkevich, Yu. G. Sobolev, O. Dorvaux, B. Gall, F. Khalfallah, M. Rousseau
A rotational band has been observed in $^{251}$Md using RITU and 
the $\\gamma$-ray spectrometer Jurogam at the University of Jyv\\\"askyl\\\"a.
Interpreted as having a $1/2^-$
configuration, this is the first firmly established rotational band in an odd-Z
transfermium nucleus.
In order to disentangle the 
single-particle structure, the $\\alpha$ decay of
$^{255}$Lr has been studied both at Jyv\\\"askyl\\\"a and at GANIL.
From the preliminary analysis, we have observed for the first time the $\\alpha$ decay
fine structure of $^{251}$Md and two excited states in $^{247}$Es.
Four $\\alpha$ lines from the $^{255}$Lr decay have been observed, 
originating from two initial
states, which establishes the ordering of the levels.

 

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