N=Znuclei: a laboratory for neutron–proton collective mode

Abstract

The neutron-neutron and proton-proton pairing correlations have long been recognized to be the dominant many-body correlation beyond the nuclear mean field since the introduction of pairing mechanism by Bohr, Mottelson and Pines nearly 60 year ago. Nevertheless, few conclusion has been reached concerning the existence of analogous neutron-proton (np) pair correlated state. One can see a renaissance in np correlation studies in relation to the significant progress in radioactive ion beam facilities and detection techniques.The np pairs can couple isospin T = 1 (isovector) or 0 (isoscalar).In the isovector channel, the angular momentum zero component is expected to be the most importance one. On the other hand, as one may infer from the general properties of the np two-body interaction, in the isoscalar channel, both the np pairs with minimum (J=1) and maximum (J=2j) spin values can be important. In this contribution, we will discuss the possible evidence for np pair coupling from different perspective and analyze its influence on interesting phenomena including the Wigner effect and mass correlations in odd-odd nuclei. In particular, we will explain the spin-aligned pair coupling scheme and quartet coupling involving pairs with maximum (J=2j) spin values.

Parameter optimization for the latest quark-meson coupling energy-density functional

“…The plot legend is located in the top left panel. N = Z nuclei are known to exhibit Wigner effect[33] that must be accounted for in the binding energy. Furthermore, the QMCπ-II parameter set predicts mostly underbinding on the neutron-rich side, as shown inFigure 3.…”

Large-scale configuration interaction description of the structure of nuclei around100Sn and208Pb

“…The α decays from N ∼ Z nuclei can provide an ideal test ground for our understanding of the np correlation. We have evaluated within the shell-model approach the nn and pp twobody clustering in 102 Sn and 102 Te and then evaluated the correlation angle between the two pair by switching on and off the np correlation [14]. If the np correlation is switched on, in particular if a large number of levels is included, there is significant enhancement of the fourbody clustering at zero angle.…”

Mass differences and neutron pairing in Ca, Sn and Pb isotopes

“…The observed even-odd mass staggering (EOS) has been extensively explored in the literature [6][7][8][9][10]. The EOS effect is generally associated with the pairing gap ∆, as suggested by BCS theory.…”