Speaker
Prof.
Thorsten Kröll
(TU Darmstadt)
Description
The neutron-rich isotope 128Cd is only two proton and two neutron
holes away from the doubly-magic nucleus 132Sn. It is famous for the
irregular behaviour of the excitation energy of the first 2+ state,
a feature which cannot be explained even by recent shell model
calculations. Currently, only a beyond-mean-field approach is capable
to reproduce the anomaly. However, it predicts a considerable prolate
deformation next to the N=82 shell closure. Astrophysical interest in
this particular isotope arises from the proximity to the r-process
waiting-point nucleus 130Cd.
We investigated the exotic isotope 128Cd for the first time by safe
Coulomb excitation. The beam was delivered at an energy of about
2.85 MeV/u by the REX-ISOLDE facility at CERN. Scattered beam particles
as well as recoiling target nuclei were detected by a segmented Si
detector in coincidence with gamma-rays measured by the MINIBALL array.
From the differential excitation cross section electric matrix elements
were deduced. In previous experiments, the isotopes 122,124,126Cd have
been investigated in a similar way and evidence for a larger quadrupole
collectivity compared to predictions from the shell model has been found.
Additionally, the isotope 126Cd has been studied in a lifetime measurement
employing the Doppler shift attenuation method (DSAM).
In this contribution we will present first new results for 126,128Cd and
discuss the evolution of the quadrupole collectivity along the Cd isotopic
chain towards N=82.
This work is supported by BMBF (No. 06DA9036I), EU through ENSAR (No. 262010),
HIC for FAIR, and the MINIBALL and REX-ISOLDE collaborations.
Primary author
Prof.
Thorsten Kröll
(TU Darmstadt)
Co-authors
Dr
Marcus Scheck
(TU Darmstadt)
Mr
Michael Thürauf
(TU Darmstadt)
Mr
Mirko von Schmid
(TU Darmstadt)
Ms
Sabine Bönig
(TU Darmstadt)
Dr
Stoyanka Ilieva
(TU Darmstadt)
Mr
Timo Bloch
(TU Darmstadt)
