Different particle alignments in N \approx Z Ru isotopes studied by the shell model
Abstract
Experimentally observed heaviest
N≈Z
nuclei, Ru isotopes, are investigated by the shell model on a spherical basis with the extended
P+QQ
Hamiltonian. The energy levels of all the Ru isotopes can be explained by the shell model with a single set of force parameters.
The calculations indicate enhancement of quadrupole correlations in the
N=Z
nucleus
88
Ru as compared with the other Ru isotopes, but the observed moments of inertia seem to require much more enhancement of quadrupole correlations in
88
Ru. It is discussed that the particle alignment takes place at
8
+
in
90
Ru but is delayed in
88
Ru till
16
+
where the simultaneous alignments of proton and neutron pairs take place.
The calculations present interesting predictions for
89
Ru that the ground state is the
1/
2
−
state and there are three
ΔJ=2
bands with different particle alignments including the T=0
p−n
pair alignment.