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



Abstract No: 039
Submitted on: 15 Jan 2001, 20:33 GMT
Title: Violation of the K-selection rules in 178Hf observed via Coulomb excitation.
Author(s): P.J.Napiorkowski,1 T.Czosnyka,1 J.Srebrny,2J.Gerl,3 Ch.Schlegel,3 H-J.Wollersheim,3D.Cline,4 C.Y.Wu,4 R.Teng,4K.Vetter5, A.Macchiavelli,5and M.Devlin 6
Affiliation(s): 1HIL, Warsaw University, Poland, 2NPD IEP, Warsaw University, Poland, 3GSI, Germany, 4University of Rochester, USA, 5LBNL, USA, 6University of St. Louis, USA



The study of the K-isomer properties with Coulomb excitation attracts recently a great interest. Experiments performed to explain the nature of the well-known long-lived isomer in 180Ta indicate the existence of the intermediate state or states, making possible to depopulate the collective structures built on the isomeric level. Despite the large difference of K quantum number between the ground state and the isomeric state such depopulation has been observed [1,2]. But intermediate states have not been identified yet.

The other approach to test the K-selection rules is to populate states in an isomeric band starting from a ground state band [3,4]. Coulomb excitation offers an unique way to search for the intermediate states because, unlike any other nuclear reaction, selectively populates the levels strongly connected to the ground state.

The Coulomb excitation experiment on the 178Hf was performed using the Gammasphere equipped with the particle detector Chico.[5] For the first time discrete transitions in the K$^\pi$=8- isomeric band excited from K$^\pi$=0+ ground state were observed. The mechanism of the excitation of the isomeric band is still an open question. It can be explained either by assuming direct E3 excitation or E1 decay from higher lying states of ground state band. The conclusions from the analysis of recent experiments are presented.

Bibliography

1
C.Schlegel et al., Phys.Rev. C50, 2198 (1994)

2
M.Loewe et al., Acta Physica Polonica B30, 1319 (1999)

3
J.H.Hamilton et al., Phys.Lett. 112B, 327 (1982)

4
H.Xie et al., Phys.Rev. C48, 2517 (1993)

5
M.W.Simon et al., Proc. of the Int. Conf. of Fission and Properties of Neutron-rich Nuclei, (Sanibel Island, FL World Scientific Publishing Co., December 1997)
D.Cline, Acta Physica Polonica B30, 1291 (1999)

\fbox{ Preferred presentation of the contribution: in the poster session. }

High Spin Conference
2001-01-16