Speaker
Andrea GOTTARDO
(CNRS)
Description
In neutron-rich nuclei, especially near shell-closures, the increasing
Q-value of beta decays and the lowering of the neutron-separation
threshold, lead to the dominance of beta-delayed neutron emission as
decay mode. At the same time, Q-values well above 10 MeV provide the
possibility to study highly-excited particle-hole states populated by
the GT decay.
A measurement was performed to study the beta-delayed neutron mission
from the decay of neutron-rich potassium isotopes. Low-energy beams of
51,52,53,54K were produced by the reaction on UCx target from the PSB
proton beam. The surface-ionized ions were delivered to the experimental
setup, which combined the ISOLDE Decay (tape) Station with the VANDLE
array for neutron spectroscopy. The IDS was equipped with a
high-efficiency beta detector and four Ge clovers. The VANDLE array was
made of 26 bars of plastic scintillators arranged in cylindrical
configuration at 1 m distance around the implantation point, giving an
overall efficiency of 10% for 1 MeV neutrons.
Beta-delayed gamma rays and neutrons from 51,52.53K were measured with
sufficient statistics to reconstruct the excited levels below and above
the neutron-separation threshold in 51,52,53K.
At the first place, this will allow one to identify particle-hole excited states which will help
to track the monopole evolution in this exotic region by measuring
excitations across the N=28 and N=32 shell and sub-shell closures. At
the second place, the GT strength distribution will be reconstructed up
to high-energy states (10 MeV and above). The production of 54K was also
demonstrated via the identification of its beta-n daughter 53Ca.
Preliminary results will be shown, with a discussion for future
perspectives at ISOLDE.
