Speaker
Prof.
Bogdan Fornal
Description
The evolution of properties of atomic nuclei with respect to increase in neutron
richness is one of the crucial issues in the modern nuclear structure studies. In
particular, neutron-rich nuclei above the doubly magic 48Ca have recently
attracted a lot of interest due to an N=32 subshell closure that was evidenced
in 52Ca, 54Ti and 56Cr. This phenomenon was attributed to the strong proton
f7/2 - neutron f5/2 monopole interaction, which causes an increase in energy of
the f5/2 single particle orbital with respect to the p3/2 and p1/2 levels as
protons are subtracted from the f7/2 shell. However, the magnitude of this
increase, particularly in Ca isotopes, is difficult to detect as the states involving
the neutron f5/2 orbital in such nuclei like 51-53Ca are very hard to reach. In
our recent experiments we studied neutron-rich species close to Z=20 using
deep inelastic processes occurring in heavy ion collisions of a 48Ca beam on a
238U target. In one measurement, a thick target technique was applied and
the gamma coincidence data were collected with GAMMASPHERE at Argonne NL.
In the second experiment, the same reaction was studied employing the
PRISMA+CLARA detection system at LNL in Legnaro. With A and Z reaction
fragment identifications obtained from PRISMA, we were able to assign the
observed (with CLARA) gamma transitions to a given product. These transitions
were subsequently used as “starting points” in the analysis of thick target
gamma coincidence data. Among many findings, yrast structures in the N=31
isotones, 52Sc and 51Ca were located - these structures include excitations
involving f5/2 neutrons. The presentation will discuss new results in light of
shell model calculations and theoretical predictions for the f7/2 – f5/2
monopole interaction strength arising from the tensor component of the
nucleon-nucleon interaction.
Author
Prof.
Bogdan Fornal
