High Spin Physics 2001, Warsaw, February 6-10, 2001



Abstract No: 010
Submitted on: 21 Dec 2000, 16:48 GMT GMT
Title: Evidence for the wobbling mode in 163Lu
Author(s): S.W. Ødegård1,2, G.B. Hagemann1, D.R. Jensen1, M. Bergström1, B. Herskind1, G. Sletten1, S. Törmänen1, J. Wilson1, P.O. Tjøm2, K. Spohr3, H. Hübel4, A. Görgen4, G. Schönwasser4, A. Bracco5, S. Leoni5, A. Maj6, C. Petrache7, P. Bednarczyk8, D. Curien8


Affiliation(s): 1The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen Ø, Denmark, 2Dept. of Physics, Univ. of Oslo, PB 1048 Blindern, N-0316 Oslo, Norway, 3Department of Electronic Engineering and Physics, Univ. of Paisley, Scotland, 4Institut für Strahlen- und Kernphysik, University of Bonn, Germany, 5Dipartemento di Fisica and INFN, Sezione di Milano, Milano, Italy, 6Niewodniczanski Institute of Nuclear Physics, Krakow, Poland, 7Dipartemento di Fisica and INFN, Sezione di Padova, Padova, Italy, 8IReS, 23 rue du Loess, BP28 F-67037, Strasbourg, France



The wobbling mode is a direct consequence of rotational motion of a triaxial body. The wobbling degree of freedom introduces sequences of bands with increasing number of wobbling quanta [1], and a characteristic $\Delta I=1$ decay pattern between the bands in competition with the in-band decay.

Favourable candidates for establishing for the first time this exotic excitation mode may be found in Lu-isotopes for which stable triaxial superdeformed shapes are expected. Several, presumably triaxial, superdeformed bands (TSD's) involving an aligned i13/2 proton, which would strongly influence the decays from a wobbling excitation [2], are reported in recent years [3].

In a search for the wobbling mode built on TSD1 in 163Lu an experiment using the fusion evaporation reaction 139La(29Si,5n) with a beam energy of 152 MeV was performed at the Euroball IV setup in Strasbourg. Several crossband transitions between a new band, TSD2, and TSD1 have been established, see the figure. From angular distribution, DCO ratio, and linear polarization measurements the mixed E2/M1 multipolarity could be deduced. Thereby firm spin and parity are



\begin{figure} \mbox{ \mbox{\psfig{figure=msu-new.ps,width=50mm,height=60mm,angl... ...servation of the long sought wobbling mode for the first time. } } \end{figure}


Bibliography

1
Å. Bohr and B.R. Mottelson, Nuclear Structure, Vol. II, (Benjamin, New York, 1975).

2
I. Hamamoto, Phys. Lett. B193 (1987) 399 and invited talk at this conference.

3
G.B. Hagemann, Phys. Scripta T88 (2000) 77 and refs. therein.
\fbox{ Preferred presentation of the contribution: in the oral session. }
High Spin Conference
2001-01-05