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



Abstract No: 009
Submitted on: 21 Dec 2000, 12:07 GMT
Title: Population of high spin states in fragmentation reactions
Author(s): M. Pfützner1, P.H. Regan2, P. Walker2, Zs. Podolyak2, M. Caamaño2, J. Gerl3, M. Hellström3, P. Mayet3, and M. Mineva4 for the GSI ISOMER Collaboration
Affiliation(s): 1Institute of Experimental Physics, Warsaw University, PL-00-681 Warszawa, Poland
2 Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, U.K.
3 GSI, Planckstrasse 1, D-64291 Darmstadt, Germany
4 Div. of Cosmic and Subatomic Physics, Lund University, SE-22100 Lund, Sweden




The use of projectile fragmentation reactions at intermediate and relativistic energies, combined with unambiguous channel selection afforded by state of the art magnetic separators, has proved to be a very sensitive technique in the study of exotic nuclei which are often inaccessible by other, more standard high-spin methods. As recently demonstrated by results from both GANIL and GSI, the application of this technique for the spectroscopy of $\mu$s isomer decays, allows the first identification of excited states in nuclei very far from stability, even with secondary beam production rates as low as a few ions per minute [1,2]. However, rather surprisingly, one of the key variables in this method, namely the population of high-spin states in fragmentation reactions, has, until now, not been systematically studied. The current work reports on measurements of the population of more than twenty isomers produced by fragmentation of 1 GeV/nucleon 208Pb at SIS/FRS facility at GSI Darmstadt. The isomers observed range from low spin example up to decays of $K=\frac{35}{2}~\hbar$ states in 179W and 181Re. The dependence of measured isomeric ratios on the number of abraded nucleons, spin and excitation energy above the yrast line will be discussed and compared with predictions from a simple, `sharp cut-off' model based on the abrasion-ablation description of the fragmentation process [3].

Bibliography

1
J.M. Daugas et al., Phys. Lett. B 476, 213 (2000).

2
Zs. Podolyák et al., Phys. Lett. B 491, 225 (2000).

3
M. de Jong, A.V. Ignatyuk and K.-H. Schmidt, Nucl. Phys. A 613, 435 (1997).

\fbox{ Invited talk. }

High Spin Conference
2000-12-21