432 research outputs found
Properties of isocalar-pair condensates
It is pointed out that the ground state of n neutrons and n protons in a
single-j shell, interacting through an isoscalar (T=0) pairing force, is not
paired, J=0, but rather spin-aligned, J=n. This observation is explained in the
context of a model of isoscalar P (J=1) pairs, which is mapped onto a system of
p bosons, leading to an approximate analytic solution of the isoscalar-pairing
limit in jj coupling.Comment: 7 pages, 3 figures, 1 tabl
Shell model analysis of the B(E2, 2+ â 0+) values in the A = 70, T = 1 triplet 70Kr, 70Br, and 70Se
The B(E2, 2+ â 0+) transition strengths of the T = 1 isobaric triplet 70Kr, 70Br, 70Se, recently measured at
the RIKEN Radioactive Isotope Beam Factory (RIBF), are discussed in terms of state-of-the-art large scale shell
model calculations using the JUN45 and JUN45+LNPS plus Coulomb interactions. In this Letter we argue that,
depending on the effective charges used, the calculations are either in line with the experimental data within
statistical uncertainties, or the anomaly happens in 70Br, rather than 70Kr. In the latter case, we suggest that it
can be due to the presence of a hitherto undetected 1+ T = 0 state below the yrast 2+ T = 1 state. Our results
do not support a shape change of 70Kr with respect to the other members of the isobaric multiple
Microscopic structure of fundamental excitations in N=Z nuclei
Excitation energies of the =1 states in even-even as well as =0 and
=1 states in odd-odd = nuclei are calculated within the mean-field
approach. It is shown that the underlying structure of these states can be
determined in a consistent manner only when both isoscalar and isovector
pairing collectivity as well as isospin projection, treated within the
iso-cranking approximation, are taken into account. In particular, in odd-odd
= nuclei, the interplay between quasiparticle excitations (relevant for
the case of =0 states) and iso-rotations (relevant for the case of =1
states) explains the near-degeneracy of these fundamental excitations.Comment: 4 pages, 4 figure
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