Nuclear Structure Studies of Microsecond Isomers Near A=100
Acta. Phys. Pol. B
A large variety of shapes may be observed in Sr and Zr nuclei of the
A = 100 region when the number of neutrons increases from N = 58 to
N = 64. The lighter isotopes are rather spherical. It is also well established that three shapes co-exist in the transitional odd-A, N = 59, Sr
and Zr nuclei. For N > 59, strongly deformed axially symmetric bands
are observed. Recently, a new isomer of half-life 1.4(2) µs was observed in
95Kr, the odd–odd 96Rb has been reinvestigated and a new high-spin isomer observed in the even–even 98Zr. These nuclei were studied by means
of prompt γ-ray spectroscopy of the spontaneous fission of 248Cm using the
EUROGAM 2 Ge array and/or measurements of µs isomers produced by
fission of 239,241Pu with thermal neutrons at the ILL (Grenoble). To allow
spectroscopic studies of isomeric states with lifetimes around 100 ns, across
a broad range of medium-heavy neutron-rich nuclei, an experiment was
performed at a neutron guide of the ILL using thermal-neutron-induced
fission. Fission fragments were identified using a small spectrometer consisting of a section to measure time-of-flight and an ionization chamber.
Isomeric γ rays emitted from complementary fragments were detected in
an array of Ge detectors.