Identification of Nilsson Orbitals in the Superdeformed Minimum of 237Pu

As the first case ever studied with high - resolution spectroscopy
for odd-N nuclei in the second potential minimum, the fission
isomers in 237Pu (t1/2 = 110ns/1.1 μs) were investigated using the
235U(alpha,2n) reaction with a pulsed alpha beam (Ealpha =24 MeV,
Deltat=400 ns) from the Cologne Tandem accelerator. A metallic 235U
target (3.7 mg/cm2)was used, where the 237Pu reaction products were
stopped and fission products were emitted in opposite directions.
The rare gamma-rays from the second potential well in delayed
coincidence with fission products were measured with the MINIBALL
spectrometer. The identified level scheme will be presented and
compared to single - particle calculations allowing for the first
time an identification of the Nilsson quantum numbers. The
identification of Nilsson orbitals will provide an important input
for the validation and improvement of theoretical nuclear models
and will lead to improved predictions for fission barriers and
their extrapolations to neutron-rich heavy elements in the mass
region of the r-process path of the astrophysical nucleosynthesis.