Speaker
Thomas James Morgan
(Ludwig Maximilians University)
Description
While so far spectroscopic studies of fission isomers concentrated on
even-even nuclei, high-resolution spectroscopy of odd-N fission isomers
will allow to identify Nilsson orbitals in heavy actinide nuclei.
As the first case ever studied for odd-N nuclei, the fission isomer in
237Pu (t1/2 = 110ns/1.1 ?s) was investigated using the 235U(alpha,2n)
reaction with a pulsed alpha beam (Ealpha =24 MeV, pulse distance 400 ns)
from the Cologne Tandem accelerator. A self-supporting thick 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 -rays from the second potential well in delayed coincidence
with fission products were measured with the MINIBALL spectrometer.
Due to the small population cross section of about 2 ?b a large solid
angle coverage both for the -rays as well as for the fission fragments
was required. A very compact 4Pi parallel plate detector array (diameter
ca. 15 cm) was used for the fission fragment detection, allowing for
a discrimination between the dominant prompt fission products and
the rare isomeric fission events. Results, such as the identification of
rotational bands, isomeric lifetimes and angular distributions etc., will
be presented. *Supported by DFG under contract no. HA1101/12-1
Author
Thomas James Morgan
(Ludwig Maximilians University)
