Speaker
Description
New data on lifetimes of excited states in the ground state band of $^{178}$W,
$^{178}$Os, and $^{182}$Os are presented. The mean lifetimes of the 2$^+_1$ and 4$^+_1$
were measured using the
fast timing method with LaBr$_3$ detectors in the $\nu$-Ball setup at the IPN Orsay
and at HORUS at the IKP Cologne. The isotopes of interest were produced in fusion-evaporation
reactions. The new results of these measurements complete the
data on B(E2) values for the 2$^+_1$ and 4$^+_1$ states in this region, which allows
the study of B(E2) evolution with neutron number in these isotopes. Emphasis is put on the different B(E2)
systematics of the W and Os isotopic chain compared to the neighbouring Hf and Yb isotopes.
Additionally, in $^{178}$W, previously unkown half lives of short lived K-isomers were measured
by taking advantage of the pulsed beam during the $\nu$-Ball experiment.
These are the 12$^+$ state at \mbox{3235 keV} and the 11$^-$ state at \mbox{3053 keV}.
Using the new experimental data, reduced transition rates and hindrance factors were calculated for these
levels for the first time.
The very low observed reduced hindrance factors of transitions from these isomers to the $10^+$ member of
the ground state band are discussed in terms of mixing with a high-K configuration t-band.
| Topic | Nuclear Structure and Nuclear Astrophysics |
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